Immediately after Andrews' morning news conference, top Democrats from across South Jersey united behind Norcross, a longtime labor union leader and the brother of Democratic power broker George E. Norcross III. George Norcross is also majority owner of the company that publishes The Inquirer.
State Senate President Stephen Sweeney (D., Gloucester) endorsed Norcross, as did Assembly Majority Leader Louis D. Greenwald (D., Camden), Camden Mayor Dana L. Redd, and the state AFL-CIO. South Jersey Democrats said U.S. Sen. Cory Booker (D., N.J.) would join the parade of endorsements.
The support gave Donald Norcross backing from almost everyone in his party with the political might to challenge him.
"I have spent my career fighting for middle-class families, senior citizens and workers," Norcross, 55, said in a statement announcing his candidacy - hours after the endorsements rolled in. He promised to work for job creation and "equal opportunity for everyone."
A Democratic district
The district is very Democratic - President Obama won 66 percent of its votes in 2012 - so the party's nominee after a June primary will be the heavy favorite in the fall.
Two other Democrats who expressed interest in running - Logan Township Mayor Frank Minor and Matthew Harris - face steep odds.
"People should have a choice," Minor said.
By contrast, three other House departures in the Philadelphia area have set off vigorous scrambles to grab a rare open seat.
Four Democrats are vying to replace U.S. Rep. Allyson Y. Schwartz (D., Pa.), who is running for governor, and numerous credible candidates have flirted with runs to replace retiring U.S. Reps. Jim Gerlach (R., Pa.) and Jon Runyan (R., N.J.).
A storied history
In moving to Dilworth Paxson, Andrews, 56, joins a firm with a storied history of political connections, where his wife, Camille, once worked. He will be barred from lobbying for a year, but will be able to advise clients on public affairs.
Andrews will depart as his profile rises on Capitol Hill - he is a close ally of Minority Leader Nancy Pelosi (D., Calif.) - but also as he awaits the results of the ethics probe that had cast a cloud over him since late 2011.
He said the new job would not be available later and would help pay for college for one daughter and medical school for the other. His daughters are 19 and 21.
"It's very much a family decision," Andrews said in an interview.
The ethics inquiry, he said at his news conference, had "no role at all."
Andrews said he had violated no rules or laws and pointed out that he was last reelected in 2012 after the issue was raised. "The people rendered their judgment," he said.
One watchdog, though, argued that all signs point to Andrews' racing out ahead of a damaging report.
"Clearly he wants to leave before there's any more embarrassment," said Melanie Sloan, executive director of Citizens for Responsibility and Ethics in Washington, a group that has long criticized Andrews' behavior.
Most retiring members of Congress stay until the end of their terms, Sloan said.
"He's leaving right in the middle, which suggests he wants to make sure this doesn't see the light of day," she said.
Andrews is being investigated for using $30,000 of campaign money to pay for a 2011 family trip to Scotland, including a stay at a five-star hotel, along with other questionable uses of campaign funds.
The House ethics committee has had the issue in its hands since April 2012, after the nonpartisan Office of Congressional Ethics found "substantial reason to believe" Andrews improperly used campaign accounts "in violation of House rules and federal law."
When Andrews resigns, the ethics committee will no longer have jurisdiction over his actions.
Sloan called for the committee to release details of its investigation, but the panel rarely does so after a lawmaker resigns.
The investigation is the latest example of how missteps saddled a lawmaker widely praised for his mix of intelligence and speaking skills.
Andrews' grasp of policy and politics made him one of Democrats' top messengers when they pushed through the Affordable Care Act. In campaigns in New Jersey, he was often picked as a sparring partner in debate preparation.
Obama, in a statement, called Andrews an "original author" of the health law who served "with tenacity and skill."
He had one dubious distinction: According to the website GovTrack, he introduced 646 bills without any becoming law.
His statewide ambitions floundered. He lost a 1997 gubernatorial bid and infuriated fellow Democrats in 2008 by taking on then-Sen. Frank R. Lautenberg in a primary.
Andrews' friends say that after that chastening loss, he focused on the House and grew in stature. The ethics probe, though, remained.
Asked Tuesday if he regretted using campaign funds for the Scotland trip, he said: "I regret creating any distraction that would take people away from the mission I brought to this office, which is to try to help the people of my community."
Since December 2011, Andrews has spent $205,735 on defense attorney Stanley Brand, campaign filings show.
Unless Gov. Christie calls a special election, Andrews' seat will be vacant until November.
Two simultaneous elections then will decide who fills the seat for rest of the current term and who begins a new two-year term in January. By joining the House in November, the winner will get a jump on seniority over other freshmen.
Andrews joined Congress in just such circumstances in 1990, when he was the party pick to replace James J. Florio, who had become governor.
Inquirer staff writer Julia Terruso contributed to this article.