Center-left think tank Third Way urgently called on the Democratic front-runners of the 2020 presidential election to challenge Sen. Bernie Sanders on the South Carolina debate stage on Feb. 25, in a memo provided to Axios' Mike Allen on Saturday.

What they're saying: "At the Las Vegas debate ... you declined to really challenge Senator Sanders. If you repeat this strategy at the South Carolina debate this week, you could hand the nomination to Sanders, likely dooming the Democratic Party — and the nation — to Trump and sweeping down-ballot Republican victories in November."

Catch up on today's biggest news:

1. Warren Buffett releases annual letter, reassures investors about future of Berkshire Hathaway
2. Centrist Democrats beseech 2020 candidates: "Stand up to Bernie" or Trump wins
3. Reports: Facebook offers up to $5 for voice recordings
4. America's future looks a lot like Nevada
5. Greyhound bars immigration sweeps

Greyhound said it will stop allowing Border Patrol agents without a warrant to board its buses to conduct routine immigration checks, AP reports.

What they're saying: The company said it'll notify the Department of Homeland Security that it does not consent to unwarranted searches on its buses or in areas of terminals that are not open to the public.

Today's Nevada caucus will foreshadow the future of American politics well beyond 2020.

Why it matters: The U.S. is in the midst of a demographic transformation, and the country's future looks a lot like Nevada's present. Today's results, in addition to shaping the 2020 race, will help tell us where politics is headed in a rapidly changing country.

Twitter has reportedly suspended about 70 accounts posting pro-Bloomberg content, the Los Angeles Times reports.

The big picture: The presidential campaign is paying Instagram, Facebook and Twitter users in California to post messages of support on their personal accounts, the Wall Street Journal reported this week. That effort could "later be deployed nationwide," per WSJ.

Retired Navy Admiral William McRaven, who oversaw the 2011 Navy SEAL raid that killed al-Qaeda leader Osama bin Laden, defended former acting Director of National Intelligence Joseph Maguire in a Washington Post op-ed on Friday.

What he's saying: "...in this administration, good men and women don’t last long. Joe was dismissed for doing his job: overseeing the dissemination of intelligence to elected officials who needed that information to do their job," McRaven writes.

Election volunteers in charge of tallying results in Saturday's Democratic caucus are being asked to sign legal agreements to keep them from hurting the reputation of the Nevada Democratic Party, the Washington Post reports.

Why it matters: These nondisparagement agreements come after Democrats used an app created by Shadow Inc. that threw Iowa's caucuses into disarray, leading to delayed results amid evidence of an error-riddled process.

Sen. Bernie Sanders told reporters at a campaign stop Friday that he was briefed by U.S. officials "about a month ago" on Russia's attempts to assist his 2020 presidential campaign, AP reports. "It was not clear what role they were going to play," he added.

Driving the news: Sanders' comments followed a Washington Post report that U.S. officials briefed Sanders on Russian efforts to help his 2020 campaign "as part of an effort to interfere with the Democratic contest."

• Stat du jour: 😀 Satisfaction "with the way things are going" in U.S. hits 15-year high
• S&P 500: 3,373.23 (👇 12.92 — 0.38%)
• 1 2020 thing: 🤐 Bloomberg offers to release women from 3 NDAs
• 1 showbiz thing: ☕️Friends reunion coming to HBO MAX in May
• 1 biz thing: 😔Wells Fargo to pay $3 billion for opening fake accounts
• 1 sports thing: 👟 Another distance running record falls with high-tech Nikes

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Mike Bloomberg said Friday his company will release women identified to have signed three nondisclosure agreements so they can publicly discuss their allegations against him if they wish.

Why it matters, via Axios' Margaret Talev: Bloomberg’s shift in policy toward NDAs comes as he tries to stanch his loss of female support after the Las Vegas debate. It is an effort to separate the total number of harassment and culture complaints at the large company from those directed at him personally. That could reframe the criticism against him, but also protect the company from legal fallout if all past NDAs were placed in jeopardy.

Former U.S. ambassador to Ukraine Marie Yovanovitch has signed a book deal with Houghton Mifflin Harcourt, the publisher told AP on Friday.

Details: The untitled memoir will detail the experiences of the career diplomat from Somalia to Kyiv before she returned to Washington, D.C.

Former New York City Mayor Michael Bloomberg has dropped in favorability days after drawing boos at his debut debate performance as a Democratic presidential candidate, according to new Morning Consult polling.

By the numbers: 17% of Democratic primary voters list Bloomberg as their top choice if a primary or caucus were held in their state — down from 20% before the Las Vegas debate. His net favorability has fallen 20 points from Morning Consult's pre-debate poll, when 25% of Democratic primary voters found him unfavorable. Now, 35% find him unfavorable.

In the last two months, Bernie Sanders has surged 20 points among college students to become the group's clear 2020 favorite, according to a new College Reaction/Axios poll.

Why it matters: The numbers reflect the extent to which young Democratic voters are embracing socialism and rejecting moderate choices.

Mike Bloomberg's campaign said Friday that vandalism at its Knoxville, Tenn., office "echoes language from [Bernie Sanders'] campaign and its supporters," even as it admitted that it didn't know who was responsible.

Why it matters: It marks a massive escalation in the war of words between the two Democratic presidential candidates that has spilled into the open over the last week — covering everything from their heart health to debate performances to electability.

The Senate Leadership Fund, a political action committee linked to Senate Majority Leader Mitch McConnell, is funding ads aimed at disrupting North Carolina's Democratic Senate primary, AP reports.

Why it matters: The seat currently held by Sen. Thom Tillis (R-N.C.) is a primary target for Democrats in 2020 as they aim to flip the Senate. The McConnell-backed ads are aimed to support state Sen. Erica Smith at the expense of former state Sen Cal Cunningham, who has the backing of the Democratic Senatorial Campaign Committee.

Bernie Sanders told CBS "60 Minutes" that he was surprised by Mike Bloomberg's lackluster performance at Wednesday's Democratic debate.

What he's saying: "If that's what happened in a Democratic debate, you know, I think it's quite likely that Trump will chew him up and spit him out."

45% of Republicans — a plurality — support President Trump pardoning Roger Stone, who was sentenced this week to 40 months in prison for crimes unearthed by the Mueller investigation, according to a YouGov poll.

Why it matters: While it's still not clear whether Trump will actually move to pardon Stone, the fact that he has a plurality of his party on board regarding the issue should only serve to enforce the president's growing sense of self-confidence following his impeachment acquittal.

President Trump said in a Friday tweet that a briefing by a top election-security official before the House Intelligence Committee last week on Russia's attempts to interfere in the 2020 election was a "misinformation campaign ... launched by Democrats in Congress."

Why it matters: Trump, who was reportedly infuriated by the event, has made moves in recent days to ensure that administration jobs are held by those loyal to him — notably at the Office of the Director of National Intelligence, which led the briefing despite Trump's assertion that it was headed by congressional Democrats.

The political action committee led by Rep. Alexandria Ocasio-Cortez (D-N.Y.) endorsed Friday a slate of female 2020 congressional candidates, including a number of women of color, in races across the country.

Why it matters: The endorsements, first reported by the New York Times, highlight that Ocasio-Cortez plans to use her fundraising ability and public profile to support candidates that back her progressive aims — and, in the case of the Texas Senate race, directly challenge the party establishment's preferred candidates.

A Defense Intelligence Agency analyst pleaded guilty to leaking classified information on a foreign country's weapon system to a reporter he had a relationship with, the Department of Justice announced Thursday.

The big picture: Henry Kyle Frese faces a maximum of 10 years in prison after he "alerted our country’s adversaries to sensitive national defense information, putting the nation’s security at risk," said Assistant Attorney General for National Security John C. Demers in a news release.

Johnny McEntee called in White House liaisons from cabinet agencies for an introductory meeting Thursday, in which he asked them to identify political appointees across the U.S. government who are believed to be anti-Trump, three sources familiar with the meeting tell Axios.

Behind the scenes: McEntee, a 29-year-old former body man to Trump who was fired in 2018 by then-Chief of Staff John Kelly but recently rehired — and promoted to head the presidential personnel office — foreshadowed sweeping personnel changes across government.

President Trump told reporters on Air Force One Thursday night that he was considering nominating Rep. Doug Collins (R-Ga.) to be his next director of national intelligence, but Collins rebuffed that offer during an appearance on Fox Business' "Mornings with Maria" on Friday.

The state of play: Trump previously hinted he would intervene in the Senate race between Collins and Sen. Kelly Loeffler (R-Ga.). The heated primary race between Collins and Loeffler has raised concerns among Republicans that Democrats could potentially win the special election for the Senate seat, the Atlanta Journal-Constitution writes.

By picking Ambassador Richard Grenell to be acting director of national intelligence, President Trump has slotted a pro-Trump warrior into the ultimate apolitical role.

What they're saying: James Clapper, the longest-serving DNI (2010-2017), tells Axios it's "very worrisome installing a partisan with no real intelligence experience in this position."

Ad-libbing at his rally in Colorado Springs, President Trump attacked "Parasite," which this month became the first non-English-language film to win the Best Picture Oscar, prompting Neon, the studio behind the film, to hit back that "he can't read."

What Trump said: "What the hell was that all about? We've got enough problems with South Korea with trade. On top of that, they give them best movie of the year. Was it good? I don't know. ... Can we get like 'Gone with the Wind' back, please? 'Sunset Boulevard' — so many great movies."

The nation's top election-security official warned the House Intelligence Committee last week that Russia is interfering in the 2020 election to help President Trump get re-elected, continuing to attempt to sow discord among the American electorate, the AP reports.

Why it matters: The warning raises questions about the integrity of the presidential campaign and whether Trump's administration is taking the proper steps to combat the kind of interference that the U.S. saw in 2016.

The State Department confirmed Friday morning the U.S. and Taliban have "reached an understanding" that starts a 7-day "reduction of violence" to be followed by a signed U.S.-Taliban agreement.

Why it matters: The Afghanistan war is the longest war in U.S. history. President Trump has previously pulled out of talks at the last minute, only to restart them.

Mike Bloomberg got into the 2020 race to stop Bernie Sanders and socialism. If he doesn't bounce back from this week's debate, he may seal the deal for both.

Why it matters: Bloomberg’s own campaign has warned that Sanders could lock up the nomination in mere weeks, thanks to rivals splitting the opposition vote. But Bloomberg’s own spending makes it harder for other rivals to cut through — and virtually assures he sucks up significant delegates.

Retired U.S. District Court Judge Shira Scheindlin, who ruled in 2013 that New York's stop-and-frisk policy violated the rights of people of color, told MSNBC that Michael Bloomberg was wrong about his involvement in the controversial program at Wednesday night's debate.

What she's saying: Scheindlin refuted Bloomberg's claim that as New York City mayor he chose to reduce how many people were stopped, saying instead that he was forced: "It wasn't because he realized, had an epiphany that it was wrong. It's because of the court rulings, that's what happened, I ruled."

The Latino Victory Fund on Thursday endorsed former Vice President Joe Biden in the 2020 Democratic race.

Why it matters: The group is the first national Latino organization to endorse Biden. The endorsement comes just days before Saturday's Nevada caucuses. Hispanics are a key voting demographic in the state and could sway the outcome of the caucuses.