Former Vice President Mike Pence filed paperwork to run for president Monday, setting up a clash with former running mate Donald Trump in an increasingly crowded battle for the future of the Republican Party.

Pence, 63, will formally announce his candidacy Wednesday in Iowa, according to people familiar with his plans.

The former vice president and Indiana governor has been laying the groundwork for a White House bid for more than a year, visiting early-voting states, giving policy speeches and promoting an autobiography. But he so far hasn’t broken out of the lower tier of 2024 GOP White House aspirants with less than 4% support in the RealClearPolitics average of polls.

Pence is offering himself as the only traditional conservative in the field who can win the GOP nomination and defeat President Joe Biden — while governing with more civility than Trump. He is touting the popular policies of the “Trump-Pence” administration while breaking from his former boss on election denialism and other issues.

Pence is targeting the Hawkeye State with its first-in-the-nation GOP caucuses because of the large number of evangelical voters who participate and his appeal to Iowans as a fellow Midwesterner.

“People know Mike Pence, they just don’t know him well,” Republican strategist Scott Reed, co-chairman of the super PAC supporting Pence, told reporters last month. “His campaign is going to reintroduce Mike Pence to the country as his own man, not as vice president, but as a true economic, social, and national security conservative — a Reagan conservative.”

But critics question whether Pence has a path to the nomination, given his inability so far to win over hard-core Trump supporters and Republicans looking for an alternative. Trump and his fervent backers haven’t forgiven Pence for defying his former boss and refusing to reject certified votes for Biden during the Jan. 6 insurrection, when the members of the mob that stormed the US Capitol chanted, “hang Mike Pence.”

Trump supporters booed Pence in his home state of Indiana in April when he was introduced at a meeting of the National Rifle Association, though he did get a standing ovation from some NRA members after his speech.

Sarah Longwell, who conducts focus groups with Republican voters and publishes the anti-Trump website The Bulwark, said there is “zero appetite” among GOP voters for Pence because many think he betrayed Trump or think he’s weak.

“There are some people who are sort of kind about him, like, ‘Oh, he seems like a nice guy, he’d make a great neighbor, but he’s never going to be president, and I don’t know why he’s still in politics,’” Longwell said.

The former vice president joins a growing GOP field that will be getting larger this week. Former New Jersey Governor Chris Christie is expected to announce his candidacy at a town hall event in New Hampshire on Tuesday, and North Dakota Governor Doug Burgum has a “major announcement” on Wednesday in Fargo.

On the same day Pence filed his paperwork, New Hampshire Governor Chris Sununu, who was weighing a bid, said he is not running for president.

“Too many other candidates who have entered this race are simply running to be Trump’s vice president. That’s not leadership; that’s weakness,” Sununu said in an opinion piece in the Washington Post. “Too many candidates are afraid to confront Trump, surrendering to his attacks. I will have more credibility speaking out against Trump as a non-candidate to help move the conversation toward the future I believe the Republican Party should embrace.”

Besides Trump, the announced major GOP candidates so far include Florida Governor Ron DeSantis, former South Carolina Governor Nikki Haley, US Senator Tim Scott of South Carolina, former Arkansas Governor Asa Hutchinson, Ohio businessman Vivek Ramaswamy, and conservative radio host Larry Elder.

Trump picked Pence — who often introduces himself as “a Christian, a conservative and a Republican, in that order” — to be his 2016 running mate to shore up support among evangelical voters. Pence served six terms in Congress and was chairman of the House Republican Study Committee and House Republican Conference before being elected Indiana governor in 2012.

Pence has tried to differentiate himself from both Trump and DeSantis, the former president’s top rival for the nomination in early polling. He’s criticized the Florida governor for escalating a fight with Walt Disney Co. over its opposition to a law limiting school instruction on gender identity, saying it is not what a conservative, limited-government Republican would do.

(Updates to add additional details, background starting in sixth paragraph)