MANCHESTER, N.H. — Call it the electability primary.
One by one, at the largest gathering of presidential candidates in New Hampshire history, 19 Democratic hopefuls made the case to party activists Saturday that they were best suited to take on President Trump in 2020.
“We cannot — and I will not — let this man be reelected,” former vice president Joe Biden forcefully told the New Hampshire Democratic Party convention.
“To beat Trump, we gotta grow our base. We need a massive voter turnout,” Vermont Senator Bernie Sanders said in an interview. “And I think we are the campaign that can do those things.”
The convention was held in the same Manchester arena where Trump himself kicked off his reelection campaign last month. The hall was filled with 1,200 delegates and thousands more activists connected with the campaigns, as they tried to woo supporters in a swing state that holds the first-in-the-nation primary. In 2016, Democrat Hillary Clinton beat Trump here by just three-tenths of a percent.
The ability of a candidate to defeat Trump is, by far, the most important issue among likely Democratic primary voters in the state. Last month, a Suffolk University/Boston Globe poll found 58 percent of New Hampshire Democratic voters wanted to nominate someone who could beat Trump, while 36 percent said they preferred a candidate who shares their values.
And over seven hours Saturday, each of the candidates addressed electability directly.
Senator Elizabeth Warren of Massachusetts demonstrated the sheer force of her supporters. Warren received — by far — the biggest reception of any candidate when she took the stage, welcomed with a two-minute standing ovation before she uttered a word. Her campaign paid for hundreds of tickets and provided supporters with thundersticks reading “Win With Warren.”
“We have to win in 2020,” Warren said in the opening minute of her remarks. “So let’s talk about how it’s done.”
Then, in what was perhaps a shot at her opponents, she cautioned the audience not to choose “a candidate we don’t believe in because we’re scared.” She added, “We can’t ask other people to vote for someone we don’t believe in.”
Outside the arena, the Sanders campaign rented an electric billboard showing how many doors its volunteers had knocked on in the Manchester area during the convention. By the end of the event, the campaign claimed to have visited 9,375 doors. Sanders won the 2016 Democratic primary in New Hampshire with 151,000 votes to Clinton’s 95,000.
In an interview at the convention, Sanders sat in front of a “Bernie beats Trump” sign and noted that polls consistently show him beating Trump in swing states. He also argued that he had the ability to increase the youth vote.
Senator Amy Klobuchar of Minnesota drew parallels between the large role independent voters play in New Hampshire and her home state, where she has won even in more conservative areas.
“Three words: Governor Jesse Ventura,” said Klobuchar, referring to the onetime independent governor of the state and onetime professional wrestler. Her point: She’s had statewide success in a region that once voted for someone quite different from herself.
Similarly, Governor Steve Bullock pointed out that he has won statewide three times in Republican Montana.
Entrepreneur Andrew Yang said the biggest question for Democrats to answer in 2020 is how Trump won in 2016 — and how to beat him next time.
Senator Kamala Harris of California noted that while Democrats were gathered “to talk about how we want to improve the country, our president is apparently golfing right now. So get your heads around that.”
That prompted her supporters to chant her new anti-Trump catch phrase: “Dude gotta go.”
Senator Cory Booker got a rousing reception after an energetic performance. “We gotta beat Donald Trump,” Booker said. “But beating Donald Trump is the floor — it is not the ceiling.”
It was hard to judge by the audience which candidate made the best case. For the most part, the remarks were given to the already converted. Most in the audience were given a ticket by a campaign and showed up specifically to hear their candidate speak.
Pondering the scene was former Colorado senator Gary Hart, who won the 1984 New Hampshire primary at a time when Democrats were searching for a candidate who could defeat Republican incumbent Ronald Reagan.
Despite all the focus on electability that year, Hart noted, the party nominated Walter Mondale, even though polls found Hart would do better against Reagan.
“Parties can be strange creatures when it comes to the whole electability question,” Hart said in an interview. “You never really know what they are going to do.”
James Pindell can be reached at email@example.com. Follow him on Twitter @jamespindell or subscribe to his Ground Game newsletter on politics: http://pages.email.bostonglobe.com/GroundGameSignUp