Montana Gov. Steve Bullock, one of the country’s only red-state Democrats to win reelection in 2016, announced Tuesday that he would join a crowded Democratic campaign field for the White House.

Bullock made his announcement in a video released early Tuesday that castigated what he called “evidence of a corrupt system all across America that serves campaign money, not the people.”

He noted that after the Supreme Court’s Citizens United decision that loosened regulations governing campaign money, he had pushed through “one of the strongest campaign finance laws in the country.”

“I believe in an America where every child has a fair shot to do better than their parents,” Bullock said. “But we all know that that kind of opportunity no longer exists for most people; for far too many, it never has. That’s why we need to defeat Donald Trump in 2020 and defeat a corrupt system that lets campaign money drown out the people’s voice so we can finally make good on the promise of a fair shot for everyone.”

He has prepared a campaign focused on his record of winning over Republican-leaning voters and lawmakers in the Mountain West with liberal policy ideas — a pattern he says will allow him to argue he is one of the most electable Democrats in the packed field.

In Montana, Bullock convinced a Republican-dominated legislature to expand Medicaid under the Affordable Care Act and put new limits on anonymous money in politics while successfully pushing a ballot initiative to raise the minimum wage and index it for inflation.

“Twenty to 30 percent of my voters supported President Trump,” Bullock said during a campaign visit Tuesday to Helena High School.

A former chairman of the Democratic Governors Association who now chairs a national group of governors, Bullock, 53, has criticized the Democratic Party for focusing too much on its base voters and not enough on reaching out to Republicans and independents. In Montana, a rural state that tends to be less polarized in its voting patterns than others are, Bullock won reelection in 2016 by four points even as Trump won the state by 20.

“Get your head around this: 20 percent of the folks that voted for me also voted for Trump,” he said in a 2018 visit to Johnston, Iowa. “To get elected and to serve in government, I have to go to a lot of places where there are not a lot of Democrats in sight. And I have to talk to people. I have to listen to people.”

Earlier this year, Bullock rebuffed an effort by Senate Minority Leader Charles E. Schumer to convince him to run for Senate in 2020. But he was forced to watch the first months of the presidential primary from the sidelines as he worked on state business through the legislative session, which ended in April.

The late start will create an early challenge in a field of 22 candidates, including another red-state contender, South Bend, Ind., Mayor Pete Buttigieg, who has also presented himself as a bridge builder. Only 20 candidates will earn a spot on the first two debate stages, starting in June, based on public polling and grass-roots fundraising prowess.

Bullock initially differed from other Democrats on gun issues, but after his reelection in 2016, he changed positions to support universal background checks for firearm purchases. In 2017, he said he would support a federal ban on semiautomatic military-style weapons. He has repeatedly vetoed bills that would set new conditions on abortion access in his state.

Bullock endorsed Hillary Clinton’s 2016 campaign, but he was a critic of her goal of quickly shifting the country to clean energy, including a promise to invest in coal country, because her policies would “put a lot of coal miners and coal companies out of business.”

Bullock later told reporters that some of her comments on coal “frustrate me.” He has since argued that it is dangerous to ignore global warming, while nonetheless stating that “there’s no way” to quit using coal over the next 15 to 20 years.

Born in Missoula, Mont., and raised in nearby Helena, Bullock graduated from Claremont McKenna College in California and New York’s Columbia Law School before returning home for a series of public jobs. He ran unsuccessfully for state attorney general in 2000, and after a brief stint as a private lawyer in Washington, D.C., he won the office in 2008.

In February, Bullock apologized after an employee he had fired following an incident of sexual harassment was accused of similar acts in his new job as an adviser to New York Mayor Bill De Blasio.

“I was wrong and naive to think I did enough,” he wrote. “I should have done more to ensure future employers would learn of his behavior.”

David Weigel reported from Helena.