WASHINGTON - Illinois Republican Rep. Aaron Schock abruptly resigned Tuesday after a monthlong cascade of revelations about his business deals and lavish spending on everything from overseas travel to office decor in the style of

Downton Abbey.

"I do this with a heavy heart," Schock said in a statement. He said he had given the people of his Peoria-area district his all since his election in 2008, "but 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."

Schock, 33, had drawn attention for his physical fitness - he once showed off his abs on the cover of Men's Health magazine - and his fund-raising. But more recently he has come under scrutiny for extravagant spending, payments to donors for flights on private jets, and improperly categorized expenses.

The questions raised have included Associated Press investigations of his real estate transactions, air travel, and Instagram use. On Monday, the AP confirmed that the Office of Congressional Ethics had reached out to Schock's associates as it apparently began an investigation.

In a statement, House Speaker John A. Boehner said: "With this decision, Rep. Schock has put the best interests of his constituents and the House first."

Schock did not inform any House leaders before making his decision. Although the questions about spending had begun to attract attention, he had not been facing concerted public pressure to step down.

Illinois Gov. Bruce Rauner will have five days from the March 31 effective date of Schock's resignation to schedule a special election, which must be held within 120 days of the vacancy.

GOP State Sen. Darin LaHood, considered the front-runner in the heavily Republican district, will announce his candidacy Wednesday, Republican officials said. LaHood is the son of Ray LaHood, who served in Congress and later as President Obama's transportation secretary.

Schock's fall was swift. Only weeks ago, a Washington Post report about his Downton Abbey-style office led to questions about his handling of expenses. The redecoration, replete with 1920s-era touches, cost $40,000 and was charged to his office; faced with questions, he repaid the expense.