COUNCIL BLUFFS, Iowa (Reuters) - Democratic presidential candidate Joe Biden will crisscross Iowa by bus for eight days starting on Saturday, the longest trek of his campaign, to make a personal appeal for support in a critical state where he has lost ground in polls.

Biden, who served as vice president to Democratic former President Barack Obama, is among a historically large Democratic field, many with better-financed operations, who are vying for the party’s nomination to face Republican President Donald Trump in the November 2020 election.

Iowa, the state that hosts the first presidential nominating contest on Feb. 3, will be a key test. Tom Vilsack, the former Iowa governor and U.S. agriculture secretary, said many of the state’s Democrats are still weighing their options.

“They’re going to be looking for somebody who, at the end of the day, understands how to move the country forward in a way that’s realistic but also progressive,” said Vilsack, who endorsed Biden earlier this month.

Public opinion polls show Biden’s one-time double-digit lead in the state has disappeared, and he is now fighting fast-rising Pete Buttigieg, the 37-year-old mayor of South Bend, Indiana, and progressive candidates U.S. Senators Elizabeth Warren and Bernie Sanders for first place.

Biden, 77, still enjoys a lead in national public opinion polls.

“It really is time to start turning over our government to a younger generation,” said Linda Murken, chair of the board of supervisors in Story County, Iowa, where Biden is expected to campaign on Wednesday. Murken has endorsed Buttigieg, saying that younger leaders may inspire younger voters and have a greater sense of urgency about climate change.

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Biden campaign manager Greg Schultz told donors earlier this month on a conference call the campaign does not have to win Iowa to secure the nomination. But Biden’s fundraising pleas underscore the need to counter a wave of ads in Iowa for Trump and Biden’s Democratic opponents.

“Our opponents’ advertising blitzes and cash-on-hand advantage have turned into real support for them in Iowa,” said one Biden campaign email to supporters last week.

Biden’s campaign ended September with under $9 million in cash on hand, trailing Trump, Sanders, Warren, Buttigieg and Senator Kamala Harris, according to the most recent filings with the U.S. Federal Election Commission.

The post-Thanksgiving holiday bus tour by Biden will cover 18 counties and more than 800 miles (1,287 km). Biden is scheduled to start it with an appearance alongside his wife, Jill, at his campaign’s field office in Council Bluffs.

“The goal is to have him connect with people one-on-one,” said campaign spokesman TJ Ducklo. “It is a very close race as we get close to voting with the four (leading) folks. And that was always the expectation.”

Biden will not be alone on the Iowa campaign trail. Buttigieg, Warren, Sanders, Harris and other candidates are all expected to campaign in Iowa at points during the same eight-day stretch.