The mushroom clouds over Hiroshima and Nagasaki have remained unreplicated for 75 years in part because the U.S. and Soviet Union — after peering over the ledge into nuclear armageddon — began to negotiate.

Why it matters: The arms control era that began after the Cuban Missile Crisis may now be coming to a close. The next phase could be a nuclear free-for-all.

House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Chuck Schumer sent a letter to Postmaster General Louis DeJoy on Thursday calling for the recent Trump appointee to reverse operational changes to the U.S. Postal Service that "threaten the timely delivery of mail" ahead of the 2020 election.

Why it matters: U.S. mail and election infrastructure are facing a test like no other this November, with a record-breaking number of mail-in ballots expected as Americans attempt to vote in the midst of a pandemic.

The coronavirus pandemic is accelerating the development of CRISPR-based tests for detecting disease — and highlighting how gene-editing tools might one day fight pandemics, one of its discoverers, Jennifer Doudna, tells Axios.

Why it matters: Testing shortages and backlogs underscore a need for improved mass testing for COVID-19. Diagnostic tests based on CRISPR — which Doudna and colleagues identified in 2012, ushering in the "CRISPR revolution" in genome editing — are being developed for dengue, Zika and other diseases, but a global pandemic is a proving ground for these tools that hold promise for speed and lower costs.

1. Global: Total confirmed cases as of 5 p.m. ET: 18,912,947 — Total deaths: 710,318— Total recoveries — 11,403,473 — Map.
2. U.S.: Total confirmed cases as of 5 p.m. ET: 4,867,916 — Total deaths: 159,841 — Total recoveries: 1,577,851 — Total tests: 58,920,975 — Map.
3. Politics: Pelosi rips GOP over stimulus negotiations: "Perhaps you mistook them for somebody who gives a damn" — Ohio Gov. Mike DeWine tests positive.
4. Public health: Majority of Americans say states reopened too quickly — Fauci says task force will examine aerosolized spread.
5. Business: The health care sector imploded in Q2 — More farmers are declaring bankruptcy — July's jobs report could be an inflection point for the recovery.
6. Sports: Where college football's biggest conferences stand on playing.

Local elections officials are sprinting to recruit younger poll workers ahead of November after elderly staff stayed home en masse to avoid coronavirus during primary elections.

Why it matters: A Pew Research analysis reports that 58% of U.S. poll workers in the 2018 midterms were 61 or older. Poll worker shortages can cause hours-long voting lines and shutter precincts.

Each day that goes by without a COVID-19 stimulus agreement is another day of worry for many in America's middle class, which was already shrinking before the pandemic began.

Axios Re:Cap digs into middle class myths and realities with Jim Tankersley, a New York Times economics reporter and author of the new book, "The Riches of This Land."

The Commission on Presidential Debates on Thursday denied the Trump campaign's request to add a fourth debate in the first week of September or move up one of the existing debates in order to get ahead of an expected surge in early voting.

The bottom line: Trump and former Vice President Joe Biden are set to debate on Sept. 29 in Cleveland, Oct. 15 in Miami, and Oct. 22 in Nashville. "If the candidates were to agree that they wished to add to that schedule, the Commission would consider that request," the organization wrote in a statement.

Ohio Gov. Mike DeWine (R) has tested positive for COVID-19 and plans to quarantine at his home for the next 14 days, his office announced Thursday. He currently has no symptoms.

Why it matters: The 73-year-old DeWine was set to meet President Trump Thursday on the tarmac at an airport in Cleveland and was tested as part of standard protocol. He is the second governor known to have contracted the coronavirus, after Oklahoma Gov. Kevin Stitt (R).

The extremely rich tend to think very highly of themselves, and of their ability to bend the world to their will. So when they start giving their money away, they tend to retain maximum control.

Why it matters: MacKenzie Scott, the ex-wife of Amazon founder Jeff Bezos, is worth about $60 billion. She pledged to give away substantially all of that money after she gained autonomy over her own wealth. Judging by her first 116 grants, she's doing so in a refreshingly radical — and humble — manner.

President Trump's Iran envoy, Brian Hook, is stepping down, Secretary of State Mike Pompeo confirmed Thursday. He will be replaced with Venezuela envoy Elliott Abrams, a noted Iran hawk who will serve in both roles.

Why it matters: Hook had been tasked with executing Trump's "maximum pressure" policy toward Iran, working closely with Pompeo. That strategy has deepened tensions and thus far failed to force Iran back to the negotiating table, as Trump had hoped.

National Oceanic and Atmospheric Administration forecasters warned Thursday of the potential for an "extremely active" hurricane season in the Atlantic.

The big picture: The agency expects 19 to 25 named storms — with three to six major hurricanes — during the six-month hurricane season, which ends Nov. 30. The average season produces only 12 named storms.

New York Attorney General Letitia James filed a lawsuit Thursday to dissolve the National Rifle Association, alleging the group committed fraud by diverting roughly $64 million in charitable donations over three years to support reckless spending by its executives.

Why it matters: The NRA is the most powerful gun lobby in the country and receives a huge amount in donations each year, but New York's investigation claims that CEO Wayne LePierre and other top leaders undermined the organization's mission for their own personal benefit.

On Sep. 23, 2013, a Russian-owned, Moldovan-flagged ship departed Georgia en route to Mozambique bearing 2,750 tons of ammonium nitrate, a material used in fertilizer as well as explosives.

Why it matters: The Rhosus made an unscheduled stop in Beirut, apparently due to engine problems. The ammonium nitrate never left the port, but destroyed it nearly seven years later, along with much of the city.

House Speaker Nancy Pelosi tore into her Republican colleagues on Thursday for their approach to negotiating the next coronavirus stimulus package, telling CNBC's Jim Cramer: "Perhaps you mistook them for somebody who gives a damn."

Why it matters: Democrats and the Trump administration have not agreed to any "top-line numbers" and remain "trillions of dollars apart," White House chief of staff Mark Meadows told reporters on Thursday.

Last month I wrote that SPACs are the new IPOs. But I may have understated it, because SPACs are also becoming the new private equity.

By the numbers: Short for "special purpose acquisition company," SPACs have raised $24 billion so far in 2020, with a loaded pipeline of upcoming offerings. U.S. buyout firms raised nearly $102 billion through the end of June — a much larger amount, but not so much larger that the two can't play on the same field.

Snapchat is rolling out a slew of new tools and features to help prepare young people to vote in the November election.

Why it matters: Snapchat has unparalleled reach into Gen Z and Millennial demographics. The tools it's building are meant to guide those specific populations to more resources to help them register to vote and form a voting plan. Other platforms focusing on voter registration are doing so with a much wider user population in mind.

French President Emmanuel Macron walked through the blast-damaged streets of Beirut on Thursday, swarmed by people chanting for the fall of Lebanon's government and pleading for international aid.

Why it matters: Lebanon is at a breaking point. Its economy was collapsing and its government hardly functioning — all before a massive explosion destroyed swathes of the capital city, including its vital port.

The 2020 PGA Championship tees off Thursday at San Francisco's TPC Harding Park, which is hosting its first-ever major.

Why it matters: It's the first major in more than a year — and the first of seven majors in the next 12 months. Though there won't be any fans in attendance, the excitement is palpable.

Even if Friday's jobs report shows a big number, it is becoming clear hiring slowed and likely even reversed course in July and real-time indicators suggest the employment situation worsened into August.

Driving the news: Payroll processor ADP's monthly jobs report showed private companies added 167,000 jobs last month, well below the 1.2 million expected by economists and far below June's 4.8 million jobs added.

After grilling the CEOs of Amazon, Facebook, Google and Apple last week, members of Congress are grappling with whether to accuse any of the firms of illegal anticompetitive behavior, to propose updating federal antitrust laws — or both.

The big picture: Congress is just one arm of government making the case against these companies. Google is expected to be the first of the firms to face possible antitrust litigation from the Justice Department before summer's end, but all four face a full-court press of investigations by DOJ, the Federal Trade Commission and state attorneys general.

The White House coronavirus task force will examine more closely just how much SARS-CoV-2 might be transmitted via aerosols, and not just from droplets, NIAID director Anthony Fauci said Wednesday at an online forum sponsored by Harvard T.H. Chan School of Public Health.

Why it matters: The longer the coronavirus can remain infectious in the air, the more likely it can infect people, particularly indoors — leading to the possible need to alter air filtration and circulation within buildings.

Call it the great retail wash. A wave of defaults, bankruptcies and evictions expected in cities across the U.S. is poised to remake the retail landscape across the country, but there may be some upside for consumers and small businesses.

Why it matters: Rather than an overnight descent into a collection of urban wastelands full of Starbucks, Amazon fulfillment centers, Chase bank branches and nothing else, the coronavirus pandemic and resulting retail apocalypse may just mean that, in major U.S. cities, less is more.

Coronavirus infections are falling or holding steady in most of the country, including the hard-hit hotspots of Arizona, California and Florida.

The big picture: A decline in new infections is always good news, but don't be fooled: the U.S. still has a very long way to go to recover from this summer's surge.

Hiroshima Mayor Kazumi Matsui on Thursday urged the international community to work together to defeat the coronavirus pandemic and warned against an increase in "self-centered nationalism," per the Washington Post.

Why it matters: He said at a remembrance service on the atomic bombing of the Japanese city that the 1918 flu pandemic killed millions as countries fighting in World War I were unable to overcome the threat together, per DPR. "A subsequent upsurge in nationalism led to World War II," he added. The U.S. bombing of Hiroshima on Aug. 6, 1945 and Nagasaki three days later contributed to the end of World War II, but tens of thousands of people died.

LeBron James responded on Wednesday night to President Trump's comments calling NBA players "disgraceful" for kneeling during the national anthem to protest racism and that he won't watch games if they knelt.

The big picture: Trump has repeatedly criticized sports players for taking the knee since 2016. But James said during a news conference, "I really don’t think the basketball community are sad about losing his viewership, him viewing the game." November's elections marked "a big moment for us as Americans," he said. "If we continue to talk about, 'We want better, we want change,' we have an opportunity to do that," he added. NBA Commissioner Adam Silver has said the league will "respect peaceful protest."

Go deeper: LeBron James forms voting rights group to inspire Black voters

Vice President Pence told the Christian Broadcast Network in an interview to be broadcast Thursday that Chief Justice John Roberts "has been a disappointment to conservatives."

The state of play: The conservative Roberts has this year sided with the Supreme Court's more liberal justices on abortion, LGBTQ discrimination and the Obama-era Deferred Action for Childhood Arrivals program.

Los Angeles Mayor Eric Garcetti announced Wednesday he's authorized the city's Department of Water and Power (DWP) to shut down utilities at locations that host large gatherings during the coronavirus pandemic.

Driving the news: Garcetti's announcement follows a fatal shooting at a house party attended by roughly 200 people last Monday, the Los Angeles Times notes.

Facebook removed a video post from President Trump Wednesday in which he claimed in an interview with Fox News that children are "almost immune" to COVID-19.

Why it matters: It’s the first time that Facebook has removed content from Trump's account for violating policies on coronavirus-related misinformation.