WASHINGTON — Rep. Aaron Schock, an Illinois Republican once eyed as a cornerstone of his party’s future, announced Tuesday that he would resign from Congress after weeks of allegations that he had misused taxpayers’ and campaign funds.

The Office of Congressional Ethics recently began a review of his spending, following news of the $40,000 makeover of his Capitol Hill office in the manner of “Downton Abbey,” the popular British period-piece television series set in the early 1900s.

Schock was also dogged by questions about whether he misused his taxpayer-funded account for inappropriate travel expenses.

“The constant questions over the last six weeks have proven a great distraction that has made it too difficult for me to serve the people of the 18th District with the high standards that they deserve and which I have set for myself,” Schock said in a statement issued by his office.

At 33, Schock becomes the youngest member of Congress to resign from office. His resignation takes effect March 31, after House Republicans have handled their annual budget outline and another key domestic policy vote, on Medicare funding. Illinois officials will have to schedule a special election to find a successor. The district, centered on Peoria, is solidly Republican and is unlikely to produce a strong Democratic contender.

Schock was barely two months into his fourth two-year term but had built a public profile that outstripped his tenure, gaining a coveted seat on the Ways and Means Committee and a place on the Republican whip team.

From the covers of magazines such as Men’s Health and a deeply cultivated social media presence, Schock wore a camera-ready smile and projected a man-on-the-go image that seemed to position him for a long future in Republican politics.

He had flirted with running for governor ahead of the 2014 election and frequently told his friends that he would like to climb the leadership ladder in the House, perhaps one day becoming speaker.

While a bid last year to assume control of the House Republicans’ national fundraising apparatus went nowhere, Schock’s fundraising prowess made him an important player in Washington. Despite coming from a largely rural district, he had raised more than $6 million for his 2012 and 2014 campaigns, an enormous sum for a young back-bencher. He also campaigned across the country for colleagues in competitive races.

Schock appeared to be preparing to weather the storm – hiring legal advisers, including a former chairman of the Federal Election Commission, and a public relations team of former senior Republican aides – to review his office’s spending and his political accounts and determine whether anything was amiss.

But the official ethics probe, revealed Monday, raised the stakes. The Office of Congressional Ethics lacks subpoena power but makes recommendations to the House Ethics Committee, which serves as the formal investigator and can punish lawmakers.

On his way to vote Monday evening, Schock rushed toward the floor with his head down and did not take questions from reporters, hovering near the back of the chamber during the roll call.

On Tuesday morning, Schock was where he could be found most days, in the House gym exercising alongside fellow lawmakers. “A happy guy,” said Rep. Kristi Noem, R-S.D., a regular workout partner, describing his demeanor.

The end came swiftly and without warning to even House leaders.

A person familiar with the deliberations said that Schock did not make the decision to retire at the behest of his legal advisers, with whom he huddled Tuesday at the Jones Day law firm near the Capitol.

Instead, Schock made the decision on his own and issued a statement before alerting House Republican leaders, according to associates familiar with the timeline of events Tuesday.

“I think he’s trying to put his constituents in front, since this stuff has overtaken the ability to do certain things,” House Majority Leader Kevin McCarthy, R-Calif., said, en route to the House floor late Tuesday afternoon. “He’s putting them first.”

Ted Mottaz, a constituent who had scheduled a meeting with Schock on behalf of an association of corn producers, said he spoke with staffers Tuesday afternoon about agricultural policy, emerging from Schock’s office to learn of the resignation.

A Republican from Elmwood, Illinois, Mottaz said it was “disappointing” to see Schock associated with the spending allegations. “I’m a ‘Downton Abbey’ fan, but that surprised me,” he said of the story on Schock’s office decor that touched off the scrutiny. “He kind of lost sight of what he was doing for us in the district.”

Schock’s saga began Feb. 2 when The Washington Post reported about the expansive office redesign modeled after the Edwardian-era BBC television series with a cult following on PBS. The interior designer offered the services for free, and that prompted liberal watchdog groups to allege that it was an inappropriate gift. Last month, Schock paid $40,000 from his personal finances to cover the cost.

That incident prompted a flurry of stories about his use of private charter planes, concert ticket purchases, trips overseas and other forms of travel. On Monday night, Politico questioned him about his apparent overbilling of the federal government and his political campaign for miles traveled in his car throughout his sprawling rural district.

Schock is reimbursing the Treasury “out of an abundance of caution,” a spokesman said, for the amount of miles that he may have overbilled for official travel in his personal car.

House Speaker John Boehner, R-Ohio, said in a statement: ” Rep. Schock has put the best interests of his constituents and the House first. I appreciate Aaron’s years of service, and I wish him well in the future.”

Illinois Gov. Bruce Rauner, a fellow Republican with whom Schock had clashed, was even more terse: “This is a sad day for the people of Illinois and the 18th District.”

By the time top House Republican leaders met late Tuesday afternoon to discuss upcoming business, Schock was barely a topic of conversation. Oregon Rep. Greg Walden, chair of the National Republican Campaign Committee, briefly discussed the process for filling the seat and then turned to other matters, according to several Republicans who were present.

Schock represents a district that has been represented by storied line of Republican lawmakers – including Abraham Lincoln in the late 1840s and Robert Michel, the House minority leader from 1981 to 1995.

Michel’s top aide, Ray LaHood, a moderate Republican in a caucus that grew increasingly conservative, represented the district for 14 years, becoming transportation secretary under President Obama after his 2008 retirement. Now, with Schock vacating the seat, one of the leading contenders to succeed him is LaHood’s son, Darin LaHood, who represents much of the district in the Illinois state senate.

A fellow Illinois Republican, Rep. John Shimkus, reflected on Schock’s abbreviated tenure. “Young man, working hard, a millennial,” he said. “He reached out to a cadre that most of us older guys can’t, brought some excitement and youth to the party. I just think what happened, happened.”

Rep. Cathy McMorris Rodgers, R-Wash., the fourth-ranking House Republican, expressed sadness. Like Schock, she has been a proponent of using social media to expand the GOP’s reach and, at age 45, has developed a kinship with many of the House’s younger conservatives.

“I’m heartbroken for him and us,” she said. “He had a lot to offer.” She paused and added, “I should probably just leave it at that.”