JUDY WOODRUFF: It was another busy weekend on the campaign trail for the more than 20 candidates vying for the Democratic presidential nomination. And, as Lisa Desjardins reports, the debate on health care reform took center stage.
LISA DESJARDINS: The 2020 Democratic candidates are trying to run on their own terms.
JOSEPH BIDEN (D), Presidential Candidate: Starting over makes no sense to me at all.
LISA DESJARDINS: For former Vice President Joe Biden, today, that meant releasing his health care plan. It would add a so-called public option, allowing all Americans to buy into a Medicare-like program run by the government. He previewed the plan this weekend in New Hampshire.
JOSEPH BIDEN: I admire the rest of the field, from Bernie to Elizabeth to Kamala, who want Medicare for all. And I would build on the Affordable Care Act, and I would make sure that anyone, there was a public option.
LISA DESJARDINS: That drew ire from Vermont Senator Bernie Sanders. In a tweet today, Sanders knocked the former V.P., pointing to his former boss, President Obama, and how Obama called Sanders' Medicare for all a good idea. As for the trail, this weekend, a tale of key states; 10 2020 hopefuls addressed a friendly crowd in Iowa Sunday.
SEN. AMY KLOBUCHAR (D-MN), Presidential Candidate: We can do better, America, when it comes to infrastructure.
LISA DESJARDINS: More than 1,000 caucus-goers turned out in balmy weather for the annual Iowa Progress Corn Feed. With just over six months until the caucuses, candidates strove to appeal to widely.
JULIAN CASTRO (D), Presidential Candidate: I want to make sure that, no matter who you are, whether you live in a big city or a small town, no matter what your background is, that you can have those kind of opportunities, too.
LISA DESJARDINS: In the next state to vote, New Hampshire, no big stage, instead, backyards, as candidates worked retail politics. Former Texas Congressman Beto O'Rourke pitched his universal early education plan at a house in Manchester:
BETO O'ROURKE (D), Presidential Candidate: We will ensure that school starts not you're 4 or 5 years old in kindergarten, but when you're 3 or 4 years old in pre-K, universal across the United States of America.
LISA DESJARDINS: And in swing state Pennsylvania, in Philadelphia, the activist left met for the annual Netroots Conference. Massachusetts Senator Elizabeth Warren was met with cheers ahead of a wide-ranging panel.
WOMAN: We love you, Liz!
SEN. ELIZABETH WARREN (D-MA), Presidential Candidate: I love you, too!
LISA DESJARDINS: Also confronting candidates, increased challenges from President Trump, calling Democrats socialists or communists, weak on security. In Iowa, South Bend Mayor Pete Buttigieg said Democrats need to stand their own ground.
PETE BUTTIGIEG (D), Presidential Candidate: If we embrace a left-wing agenda, the president is going to say we're socialists and we're for open borders. If we adopt a conservative agenda, the president is going to say we're socialists and we're for open borders. So we might as well just stand up for what we believe in and take it from there.
LISA DESJARDINS: For the PBS NewsHour, I'm Lisa Desjardins.