JUDY WOODRUFF: But first: On the campaign trail this weekend, the 2020 presidential hopefuls largely avoided the topic of impeachment, as we were just discussing, with one exception. Yamiche Alcindor has the latest. On Saturday in New Hampshire, Elizabeth Warren said one word most other presidential candidates are avoiding.
SEN. ELIZABETH WARREN (D-MA), Presidential Candidate: I have called on the House to initiate impeachment proceedings.
YAMICHE ALCINDOR: The Massachusetts senator is the only 2020 candidate calling for President Trump to be impeached. She is one of just a handful of Democrats supporting such a move. Her announcement came after the public release of the Mueller report. It outlined the president's numerous attempts to block or influence the special counsel's investigation into potential ties between his 2016 campaign and Russia. While the probe didn't find outright conspiracy, it didn't exonerate Mr. Trump on the matter of obstruction.
SEN. ELIZABETH WARREN: We cannot be an America that says it is OK for a president of the United States to try to block investigations into a foreign attack on our country or investigations into that president's own misbehavior.
YAMICHE ALCINDOR: Julian Castro said the Mueller report could be a road map for impeachment.
JULIAN CASTRO (D), Presidential Candidate: I think it would be perfectly reasonable for Congress to open up those proceedings.
YAMICHE ALCINDOR: In Londonderry, New Hampshire, on Saturday, South Bend Mayor Pete Buttigieg.
PETE BUTTIGIEG (D), Presidential Candidate: That's for Congress to work out. I'm pretty sure he deserves to be impeached.
YAMICHE ALCINDOR: But some Democratic candidates, like New Jersey Senator Cory Booker, have come out against impeachment. Instead, this weekend in Nevada, Booker focused on issues like his affordable housing bill.
SEN. CORY BOOKER (D-NJ), Presidential Candidate: That alone will create more demand and hopefully would increase the supply of housing.
YAMICHE ALCINDOR: Hawaii Congresswoman Tulsi Gabbard said the report largely cleared Mr. Trump's name, and it's time to move on.
REP. TULSI GABBARD (D-HI), Presidential Candidate: The conclusion that came from that Mueller report was that no collusion took place. I'm running for president now. I don't think that we should defeat Donald Trump through impeachment.
REP. SETH MOULTON (D-MA), Presidential Candidate: I'm here to tell you and to tell America that I'm running for president of the United States.
YAMICHE ALCINDOR: Meanwhile, Congressman Seth Moulton is the latest Democrat to launch a presidential bid. He's a three-term representative from the Boston suburbs and was a Marine in the Iraq War. His take on impeachment? The debate over it should have started a long time ago.
REP. SETH MOULTON: I don't think it's the right time to have a vote on impeachment until we get all the evidence out there. But we should be having this debate. And, frankly, we should have been having it starting last year.
YAMICHE ALCINDOR: Although Warren began this debate on impeachment, a campaign aide told the NewsHour the senator will stay focused on rolling out policies. And right on cue today she debuted another detailed policy proposal. This one outlines her plans to cancel most student debt. The sweeping higher education plan impacts America's $1.5 trillion student debt crisis. It cancels up to $50,000 in student loan debt for about 42 million Americans and it invests in debt-free college. It's estimated cost is $1.25 trillion over a decade, paid for by Warren's proposed ultra-millionaire tax. This week, the crowded Democratic primary is expected to gain one more high-profile candidate. It's reported that former Vice President and longtime Delaware Senator Joe Biden will announce his candidacy on Wednesday. For the PBS NewsHour, I'm Yamiche Alcindor.