(Jenny Starrs/The Washington Post)

House Oversight and Government Reform Committee Chairman Jason Chaffetz announced Wednesday that he will not run for reelection to his House seat in 2018.

The Utah Republican said he won’t seek any political office in 2018, stirring speculation that he may run for governor in 2020. Last year, he told the Deseret News of Salt Lake City that he would “take a serious, serious look” at a gubernatorial bid in Utah once his term as chairman of the House’s primary investigative committee expired.

Chaffetz, who was first elected in 2008 and has considered running for the Senate, is the target of rising criticism over his lack of interest in aggressively investigating President Trump.

He said Wednesday that he plans to return to the private sector, though he did not provide more detail.

“For those that would speculate otherwise, let me be clear that I have no ulterior motives,” Chaffetz, 50, wrote on his Facebook page.

“I am healthy. I am confident I would continue to be re-elected by large margins. I have the full support of Speaker Ryan to continue as Chairman of the Oversight and Government Reform Committee. That said, I have made a personal decision to return to the private sector.”

He added, “I may run again for public office, but not in 2018.”

He is one of nine House Republicans who have resigned or announced plans to retire in 2018, four of whom left to join Trump’s administration and sparked special elections such as the one in Georgia on Tuesday in which Democrat Jon Ossoff nearly avoided a runoff for Health and Human Services Secretary Tom Price’s old House seat.

Anti-Trump energy has buoyed Democratic hopes of retaking the House in the midterm elections next year, and a well-funded Democratic challenger has emerged in Utah’s 3rd Congressional District, which is now open. Although it’s red territory that Chaffetz has easily won previously, 2018 dynamics could make it more competitive.

First-time candidate Kathryn Allen (D) touted her campaign on Twitter on Wednesday as news of Chaffetz’s decision spread.

“This changes the field but not my commitment to bringing integrity to Congress,” she wrote. “Since he won’t do his job, I will.”

Chaffetz has made his mark on the House since his election nine years ago and ascension to the Oversight Committee chairmanship in 2015. As chairman, he was a pugnacious prosecutor of the Obama White House and then-Secretary of State Hillary Clinton, taking a lead role in challenging the administration on the deaths of embassy personnel in Benghazi, Libya, and relentlessly probing Clinton’s private email server.

He intended to expand his oversight of the new president — if Clinton had won in November.

“It’s a target-rich environment,” the Republican said in an interview at the end of October. “Even before we get to Day One, we’ve got two years’ worth of material already lined up. She has four years of history at the State Department, and it ain’t good.”

Instead, Trump won the election, and Chaffetz has not subjected him to the aggressive oversight called for by Democrats and ethics watchdogs over possible conflicts of interest raised by the president’s sprawling business empire.

His first request to the Trump White House came in mid-February, when he asked for information about security at the president’s Mar-a-Lago estate in Florida after Trump pored over documents related to North Korea on the club’s outdoor terrace.

The move was interpreted as a small concession to critics but failed to quiet them after Chaffetz said on the same day that he would not investigate Trump’s former national security adviser, Michael Flynn, who had just resigned. The situation with Flynn was “taking care of itself,” Chaffetz said.

He eventually joined his Democratic counterpart, Rep. Elijah E. Cummings (Md.), to request information about Flynn’s security-clearance applications.

Chaffetz waffled on his support for Trump before the election, stating emphatically that he couldn’t look his teenage daughter in the eye if he backed the GOP nominee following his lewd comments toward women revealed in an “Access Hollywood” video. But a few weeks later, Chaffetz backtracked, saying he would vote for Trump because he just couldn’t stomach Clinton.

His district reelected him with 74 percent of the vote last year, but Allen outraised the congressman by collecting $534,000 as of the last filing deadline. The Salt Lake Tribune reported that Allen’s contributions spiked after Chaffetz appeared on national television and suggested that low-income Americans would be able to afford health insurance if they chose to forgo new iPhones, a comment he later tried to soften.

Republican Damian Kidd is also considering running for Chaffetz’s seat, saying Chaffetz was too interested in media attention.

This month, Chaffetz held a town hall meeting during which an angry crowd criticized his tenure as Oversight chairman. Chaffetz has faced several angry demonstrations in his district since Trump’s election but in February dismissed the protesters as a “very, very small minority” that is “not representative of the average person, certainly not in Utah.”

Lisa Rein and Mike DeBonis contributed to this report.