WASHINGTON -- U.S. Sen. Robert Menendez is getting a well-funded challenger as Bob Hugin, who recently retired as executive chairman of the pharmaceutical company Celgene Corp., plans to seek the Republican nomination to oppose the New Jersey Democrat.

Hugin, 63, will kick off his campaign Tuesday with appearances in Springfield and Delran.

"Bob Hugin has lived the American Dream," said Hugin's deputy campaign manager, Sarah Neibart.

"He is running for U.S. Senate to be an independent voice for New Jersey and to ensure that people in every community in our state can build better lives for themselves and their families. He will be a senator that New Jersey can be proud of."

Hugin's entry into the race will give Menendez, whose poll ratings plummeted before the Justice Department dropped its corruption case against him, an opponent capable of spending plenty of his own money to wage a competitive race.

Still, Menendez remains a strong favorite for re-election, said Patrick Murray, director of the Monmouth University Polling Institute.

"I don't think anybody in Washington has moved the needle on New Jersey right now," Murray said. "Menendez will be able to raise plenty of his own money. He's a great campaigner and it's a Democratic year. History suggests he will be able to overcome the drop in his approval ratings caused by the trial."

Inside Elections, a Washington-based publication that tracks congressional races, continues to rate the contest as "solid Democratic."

Nathan Gonzales, editor and publisher, said the GOP was more concerned about keeping Republican-held Senate seats in Arizona and Nevada and ousting Democrats in states that supported Trump in 2016 than in playing in New Jersey.

"The burden of proof is on Republicans to demonstrate this is a real shot," Gonzales said. "They have at least 10 better takeover opportunities before they even get to New Jersey."

Hugin grew up in Union City, was the first member of his family to attend college, and served in the Marines after graduation.

He joined Summit-based Celgene in 1999 where he rose through the executive ranks at Celgene to eventually become president and then chief executive officer. Neibart said Hugin "helped create thousands of high-skill jobs."

Hugin was a major financial backer of Gov. Chris Christie's unsuccessful presidential campaign, contributing $2,700 to his campaign committee, $5,000 to his leadership political action committee, and $250,000 to his aligned super PAC, according to the Center for Responsive Politics.

He then followed the governor's lead and contributed to Donald Trump, one of the few Christie donors to do so. He gave Trump $5,400 and donated $233,200 to the Republican National Committee, Federal Election Commission records show.

Hugin's support of Trump contrasts with a recent Gallup poll that gave the president a 61 percent disapproval rating in the Garden State, with just 34 percent approving. Residents of only eight other states thought less of Trump than those living in New Jersey.

"Bob Hugin would be a vote for Donald Trump and a vote for Trump's attacks on New Jersey: a vote for Trump is the last thing New Jersey wants from their U.S. senator," Menendez senior political adviser Mike Soliman said.

Hugin's ability to pour millions of his own money into his race will help Republicans hold onto their five U.S. House seats, Murray said.

"The big deal is here is the Republican establishment is happy, not because they will able to take Menendez's seat but he will keep this from being a complete bloodbath, which will help them down ballot as they fight to protect House seats and local offices," Murray said.

Menendez has raised $5.9 million for his re-election and entered January with $4.1 million in the bank. He had twice that amount, $8.2 million, going into 2012, his last re-election campaign.

After Menendez's first trial ended in a mistrial and a U.S. District Court judge dismissed some of the charges against him, the federal government decided not to try him again.

The Senate Ethics Committee is investigating the allegations that he intervened with federal agencies on behalf of Dr. Salomon Melgen, a friend and campaign donor, in exchange for trips and contributions.

The trial, though, took its toll on the senator's popularity. After the mistrial, 51 percent of New Jersey adults in a Rutgers-Eagleton poll last November said Menendez should not be re-elected, while 26 percent said he should. And by 49 percent to 40 percent, they said he should resign.

"I don't think Democrats are going to let this seat fall into Republican hands," Gonazles said, "Even though the trial is over, if the senator's numbers fall to a point where party officials believe the seat is jeopardy, I think you'll see Plans B or C invoked."

That's what Democratic officials did in 2004 when they replaced ethically challenged U.S. Sen. Robert Torricelli with former U.S. Sen. Frank Lautenberg a month before the election.

Menendez faces a primary challenge from Democratic activist Michael Starr Hopkins. He raised $26,268 and had $11,731 to spend as of Dec. 31.

Businessman Rich Pezzullo, who earlier announced his candidacy for the Republican nomination, raised $12,663, lent himself $100,000, and had $103,045 in the bank.

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.