WASHINGTON — House Oversight and Government Reform Committee Chairman Jason Chaffetz announced Wednesday he will not run for re-election 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 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 had expired.

Chaffetz, who has also considered running for the Senate, said Wednesday he will 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, R-Utah, 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 said.

Chaffetz, 50, was first elected to the House in 2008 and became Oversight chairman in 2015. He undertook a wide range of probes during the Obama administration but has been criticized for inaction since President Donald Trump’s election.

Running for re-election might have proved more challenging than Chaffetz wished.

Though his district is conservative, electing him with 74 percent of the vote last year, Chaffetz had already attracted a Democratic challenger for 2018: first-time candidate Kathryn Allen, who has outraised the congressman by collecting $534,000 since the start of the year. The Salt Lake Tribune reported that Allen’s contributions spiked after Chaffetz appeared on national television and suggested low-income Americans would be able to afford health insurance if they chose to forgo new iPhones, a comment he later tried to walk back.

Republican Damian Kidd also is considering running for Chaffetz’s seat, and he had pointed to his choice to withdraw, then reinstate his support for Trump last year. After archival footage from “Access Hollywood” caught Trump making lewd comments about women, Chaffetz said he couldn’t look his 15-year-old daughter in the eye and vote for the businessman. He later reversed himself and voted for Trump.

Wednesday’s announcement capped an eventful few months for Chaffetz.

In early February, he scrapped legislation to sell 3.3 million acres of federal land after a backlash from hunters and outdoors groups.

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

Protesters’ primary complaint is Chaffetz’s unwillingness to aggressively investigate the Trump administration and the potential conflicts of interest that come with Trump’s sweeping business empire. Their concern was reflected in a recent Salt Lake Tribune cartoon that depicted Trump as Jabba the Hutt, with a miniature Chaffetz sitting in his lap. The cartoon was titled: “Republicans refuse to investigate Trump’s shady dealings.”

Chaffetz was more aggressive during the Obama administration, eagerly probing the Secret Service, the Internal Revenue Service, the Bureau of Alcohol, Tobacco, Firearms and Explosives, and Hillary Clinton’s private email server.

In the last year, he has led a movement among members of the conservative Freedom Caucus to impeach Internal Revenue Service Commissioner John Koskinen, whom he accused of erasing back-up tapes containing thousands of emails written by IRS officials in a scandal over scrutiny of conservative groups. The campaign has sputtered without support from House leadership.

The District of Columbia has been a frequent target for Chaffetz. Recently, he led the Oversight Committee in a vote to block a D.C. law allowing assisted suicide and he warned D.C. Mayor Muriel Bowser not to use local tax dollars to defend illegal immigrants from deportation. He infuriated local residents when he said the District should rejoin Maryland in order to gain votes in Congress.

Chaffetz has also taken a hard line on misconduct by federal employees, particularly sexual harassment, and he is leading a nascent effort to overhaul the federal civil service under Trump.

His first request to the Trump White House came in mid-February, when he asked the White House for information about security at Mar-a-Lago 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 he would not investigate Trump’s ex-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 Cummings of Maryland, to request information about Flynn’s security clearance applications.

A frequent face on cable news, Chaffetz is known among House Republicans for his ambition.

In 2015, he launched a quixotic bid to succeed former Speaker John Boehner, R-Ohio, before stepping aside when Rep. Paul Ryan, R-Wisconsin, said he was willing to run for the position.

Chaffetz mounted his bid when Majority Leader Kevin McCarthy, R-California, whom he had called a good friend, was favored to win. The decision earned a swipe from former Republican Utah Gov. Jon Huntsman, who once employed Chaffetz as his campaign manager and chief-of-staff. Their relationship deteriorated after Chaffetz endorsed Mitt Romney over Huntsman in the 2012 Republican presidential primary.

“McCarthy just got ‘Chaffetzed.’ Something I know a little something about,” Huntsman tweeted.

Last year, Trump’s election seemed to catch the Utah Republican off-guard. Before Nov. 8, Chaffetz told The Post he was readying “years” of investigations into Clinton’s background and work as secretary of state. “It’s a target-rich environment,” he said, seeming to assume Clinton would beat Trump. “She has four years of history at the State Department, and it ain’t good.”

It is unclear who will replace Chaffetz as Oversight chairman when he leaves Capitol Hill.

Rep. John Duncan, Tennessee, is the second-most senior Republican on the panel, but he also holds seniority on the House Transportation and Infrastructure Committee, where he might prefer to claim the gavel once Rep. Bill Shuster’s, R-Pennsylvania, term as chairman ends. The next most senior Republican is Rep. Jim Jordan, R-Ohio, a conservative firebrand who lost the chairmanship to Chaffetz in a four-way race in 2014. The other two candidates were Rep. Mike Turner, R-Ohio, and then-Rep. John Mica, R-Florida.

Washington Post writers Lisa Rein and Mike DeBonis contributed.