Rep. Tom Marino (R-Pa.) (Susan Walsh/AP)

Rep. Tom Marino (R-Pa.), who was just elected to a fifth term, announced Thursday that he is resigning from Congress this month to accept a job in the private sector.

“As of January 23, 2019, I am officially stepping down from Congress,” Marino said in a statement. “Having spent over two decades serving the public, I have chosen to take a position in the private sector where I can use both my legal and business experience to create jobs around the nation.”

The former prosecutor was one of the first House Republicans to endorse Donald Trump for president and he was an informal adviser to the candidate. Marino has won handily in his heavily Republican district but faced a new reality as Democrats seized majority control of the House in November.

President Trump nominated Marino to be the nation’s drug czar in 2017, but Marino withdrew from consideration following a Washington Post/“60 Minutes” investigation detailing how the lawmaker helped steer legislation through Congress that weakened the Drug Enforcement Administration’s ability to go after drug distributors, even as opioid-related deaths continue to rise.

Marino’s 12th Congressional District, as drawn by a panel of judges last year, covers a large and deeply conservative swath of north and central Pennsylvania.

He was first elected in 2010 to represent much of the same territory, in what was at the time the most Republican-leaning Pennsylvania district represented by a Democrat.

Chris Carney, a moderate Democrat who worked on counterintelligence for the George W. Bush administration, won the seat in 2006 after Don Sherwood, a formerly safe Republican incumbent, was revealed to have conducted a years-long affair.

Carney won that election narrowly, then secured a second term in 2008 by running far ahead of Barack Obama. But Marino defeated Carney by 10 points and held onto the seat comfortably after two rounds of redistricting. In 2016, Trump carried the current district with 66.1 percent of the vote, one of his strongest performances anywhere in the state. Two years later, even as Democrats swept the state, Marino won his final term by 32 percentage points.

Marino’s departure will leave the GOP with 198 seats, as the outcome of the House race in North Carolina remains unresolved. Pennsylvania’s governor will have to set a date for a special election to fill the seat.