Elizabeth Warren enters the 2020 presidential race

Massachusetts Democrat Sen. Elizabeth Warren is launching an exploratory committee for president as she gears up for a 2020 presidential election bid, she announced in a new video on Monday.

Why it matters: Warren is the first prominent Democratic contender to launch this process.

Between the lines: Warren came under fire in the last couple of months after releasing a DNA test showing she is between 1/64th and 1/1,024th Native American. Per the Associated Press, Warren said in an email to supporters that she'd make a more formal announcement at the beginning of the new year.

One more thing: The Federal Exchange Commission, which Warren will file paperwork with to establish the committee, is closed due to the government shutdown.

What's next

New York Times endorses Elizabeth Warren and Amy Klobuchar for president

Democratic presidential candidates Sens. Elizabeth Warrenand Sen. Amy Klobuchar at the December 2020 debatein Los Angeles. Photo: Justin Sullivan/Getty Images

The New York Times editorial board has endorsed Sens. Elizabeth Warren and Amy Klobuchar for president, in a decision announced on national television Sunday night.

Why it matters: The board writes in its editorial that its decision to endorse two candidates is a major break with convention that's intended to address the "realist" and "radical" models being presented to voters by the 2020 Democratic field.

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What's next in the impeachment witness battle

Sens. Susan Collins (R-Maine) and Lisa Murkowski (R-Alaska). Photo: Tom Williams/CQ-Roll Call, Inc via Getty Images

Senators will almost certainly get to vote on whether or not to call impeachment witnesses. The resolution laying out the rules of the trial, which will be presented Tuesday, is expected to mandate that senators can take up-or-down votes on calling for witnesses and documents.

Yes, but: Those votes won't come until the House impeachment managers and President Trump's defense team deliver their opening arguments and field Senators' questions.

Inside Trump's impeachment strategy: The national security card

White House counsel Pat Cipollone and acting Chief of Staff Mick Mulvaney. Photo: Jabin Botsford/The Washington Post via Getty Images

Trump officials say they feel especially bullish about one key argument against calling additional impeachment witnesses: It could compromise America's national security.

The big picture: People close to the president say their most compelling argument to persuade nervous Republican senators to vote against calling new witnesses is the claim that they're protecting national security.