WASHINGTON — U.S. Rep. Frank LoBiondo will not seek reelection next year, he announced Tuesday, ending a career that spanned more than two decades in Congress and creating a big opening for Democrats as they try to gain control of the House.

Election analysts said LoBiondo's retirement would move the South Jersey seat from safely Republican to a pure toss-up — and South Jersey's powerful Democratic leader, George E. Norcross III, quickly announced his full support for one Democrat likely to enter the race, putting significant political muscle behind the push to flip the seat.

LoBiondo, a Republican, represents a swing district that sprawls across South Jersey and the Shore, one that supported Barack Obama twice but also backed President Trump by 5 percentage points last year.

He joins the ranks of several moderate Republicans heading for the exits, including Pennsylvania's U.S. Rep. Charlie Dent.

"Those of us who came to Congress to change Washington for the better through good governance are now the outliers," LoBiondo said in a statement. "We previously fought against allowing the perfect to become the enemy of the good. Today a vocal and obstinate minority within both parties has hijacked good legislation in pursuit of no legislation."

State Sen. Jeff Van Drew, a Democrat, said Tuesday afternoon he was interested in running for the open seat, even as he hoped to win reelection in state legislative races.

"Yes, I am interested, and certainly it's worth evaluation on my part, and [I] will look into it, although right now I'm focused obviously on the state Senate and the election that's occurring today," Van Drew said. "I would just want a little bit of a rest from all the campaigning and everything that's happened here and to also think it through."

He said he expects to decide "in a relatively timely way."

Norcross, in a statement, said he encouraged Van Drew to run and "pledged my full support."

That commitment is potentially significant. The powerful Democratic operation that Norcross leads dominates South Jersey elections, but only rarely expends much energy on congressional contests. One New Jersey Democrat said Van Drew is expected to run.

Democrats for years have hoped Van Drew would challenge LoBiondo.

LoBiondo, 71, said his decision was not based on his health or his electoral prospects. Rather, he cited the difficulty in advancing legislation and the term limit on his seat as chairman of the House subcommittee that oversees aviation issues.

"For a boy who grew up on a farm in Rosenhayn and looked to his father as a role model of how to do the right thing for the right reason, it has been a privilege to be South Jersey's voice in Congress," LoBiondo said in his statement.

In recent years LoBiondo has often been at odds with his party's most unyielding voices. He voted against the GOP's bill to repeal and replace the Affordable Care Act earlier this year and has said he would oppose the pending Republican tax plan as it currently stands. But he still drew protests from left-leaning voters who wanted him to hold more public events and speak out more forcefully against President Trump.

Two Democrats had already filed to challenge him: Sean Thom and Tanzie Youngblood.

It was not immediately clear which Republicans might run. LoBiondo's retirement caught some party leaders by surprise.

LoBiondo's retirement was first reported by Shore radio host Harry Hurley.