In a nearly hour-long exercise in pre-caucus framing, Sanders said the campaign believes the race is “going to be close” but that it would be a “gross mistake” to “not give credence and space for New Hampshire, Nevada and South Carolina.”

The Biden campaign has long tempered expectations in Iowa, where Bernie Sanders is surging and three other candidates — Elizabeth Warren, Pete Buttigieg and Amy Klobuchar — are also in contention with Biden. And Sunday was no different.

“We have always said it was going to be close,” Sanders said. “We have always said this was going to be a fight. I don’t think some people believed us when we said that.”

Biden is hardly weak here. He is running second to Sanders in the Real Clear Politics polling average, and many observers expect him to outperform his polling in the caucuses — where supporters of moderate candidates who fail to meet a 15 percent viability threshold may migrate to him on a second ballot.

“People have been writing his campaign off since the day he announced,” said former Sen. Chris Dodd (D-Conn.), a former presidential candidate and a supporter of Biden who joined Sanders and Iowa Attorney General Tom Miller for the round table in Des Moines. “Here we are the day before the caucuses, and it’s going to be a close finish based on … everything I’ve heard in the few days I’ve been here. So, Joe Biden is anything but doomed. And that was the mentality of an awful lot of people writing about his candidacy.”

He said of Biden, “He’s durable.”

Sanders, Dodd and Miller lauded Biden’s political strengths, including his retail skills and appeal nationally, where Biden is the frontrunner.

In Iowa, Sanders said people canvassing for Biden are asking voters who support another candidate to consider Biden as their second choice. The campaign is likely to benefit from second-choice votes in precincts where Klobuchar and Buttigieg — two other moderates — fail to meet the 15 percent threshold.

Miller said he has seen a “steady movement” toward Biden in recent weeks. Sanders suggested the importance of nominating a candidate with a demonstrated ability to “build a broad and diverse coalition,” a reference to Biden’s strength — and some other candidates’ weakness — with black voters who will weigh in later in the nominating process. And she disputed that there is an “enthusiasm deficit” for Biden.

“Yes, fine, Joe Biden doesn’t overwhelmingly win the youngest voters,” Sanders said. “But if we’re only looking at these voters and these young people through the prism of Twitter, I think we’re missing it.”

Asked Sunday about Biden’s advanced age — he is 77 — Dodd mentioned another politician, Nancy Pelosi, who will turn 80 this year and is doing a “hell of a job.”

“Point being,” he said, “this is the new 50, in a sense.”