Senator Menendez, on Trial, Files to Run for Re-election as an Independent

Senator Robert Menendez of New Jersey, a lifelong Democrat who is in his fourth week of a federal bribery trial, filed paperwork Monday to run for re-election as an independent in November.

The specter of Mr. Menendez, 70, trying to mount a comeback campaign raises the possibility of a splintered Democratic vote in November’s election, creating a wider lane for the Republican nominee at a time when Democrats are struggling to retain their narrow majority in the Senate.

Mr. Menendez has been abandoned by most of the state’s leading Democrats, who quickly called on him to resign after he was indicted on corruption charges last year. He has defiantly refused to step down, but he opted not to run in Tuesday’s Democratic primary.

He never, however, shut the door to running as an independent — enabling him to continue to raise and spend campaign contributions on lawyers hired to defend him and his wife, Nadine Menendez, who is also charged in the bribery conspiracy.

His trial is likely to last for at least another month; he has until the middle of August to withdraw from the Nov. 5 election.

The Democratic front-runner for Mr. Menendez’s seat, Representative Andy Kim, was quick to criticize the embattled senator’s entry into the race as selfish.

“Everyone knows Bob Menendez isn’t running for NJ families,” Mr. Kim wrote on social media. “He’s running for himself. People are fed up with politicians putting their own personal benefit ahead of what’s right for the country.”

Spokesmen for Senator Chuck Schumer, Democrat of New York and the majority leader, and the Senate Democrats’ campaign arm in Washington both declined to comment. Mike Berg, a spokesman for the Republicans’ national campaign operation, said the party was “keeping a close eye on New Jersey.”

Several Republicans are competing for the nomination in Tuesday’s Senate primary. Democrats outnumber Republicans in New Jersey by more than 900,000, and it has been a half century since voters elected a Republican to the U.S. Senate.

The move leaves Mr. Menendez’s son, Representative Rob Menendez, in an awkward position on the eve of his Democratic primary against Ravi Bhalla, the mayor of Hoboken, N.J. Representative Menendez, 38, has worked to distance himself from his father’s legal trouble and has not been accused of wrongdoing.

An aide to the congressman had no immediate comment on the senator’s plans or on how they might affect his son’s ability to win re-election to a second term in the House.

It’s unclear how the senator would successfully run a campaign. He has no paid campaign staff and a rapidly dwindling campaign war chest. His chief of staff, Jason Tuber, is leaving for a job as a lobbyist for a New Jersey-based snack manufacturer, and two of his top Senate communications staff members quit months ago.

He has spent at least $3 million of his campaign contributions on lawyers working to defend him against charges that he meddled in criminal investigations in New Jersey, steered aid to Egypt and obstructed justice by trying to make bribes appear to be loans.

Independent candidates for federal office need to collect at least 800 valid signatures to appear on the ballot; opponents have until June 10 to challenge their validity.

People familiar with the filing said that many of Mr. Menendez’s signatures appeared to be from residents of northern Hudson County, where he was raised and where he got his start as a politician, as mayor of Union City.

Indeed, on Friday night, he was in Union City eating at one of his favorite Cuban restaurants, La Gran Via.

“He’s a friend for a long time in this place,” an owner of the restaurant, Alfredo Guardado, said.

Coincidentally, the current mayor of Union City, Brian Stack — one of Representative Menendez’s biggest campaign boosters — was eating there at the same time, Mr. Guardado said.

The two men did not dine together.

Nicholas Fandos and Erin Nolan contributed reporting.