In off-season, big political calculations in N.J.

As a young man out to expose the corrupt political establishment in Union City, N.J., Robert Menendez wore a bulletproof vest as he led a slate of reformers "to clean up the city," according to his official bio.

Now that the six-term Democratic congressman is expected to be tapped by Gov.-elect Jon Corzine (D) to replace him in the US Senate, Mr. Menendez will probably have to prepare for another major fight.

While he would make history as the first Hispanic senator from New Jersey, it could be a short tenure. He has to run to be elected in his own right in 2006, and the Republicans - as well as a few local Democrats who may challenge him in the primary - want that seat. And they want it badly.

New Jersey hasn't had a Republican senator since 1977. And with the Senate closely divided along partisan lines, the Republican National Committee has already targeted the state and started raising money for a favorite son, state Sen. Thomas Kean Jr. He's the son of former Gov. Thomas Kean, who has also been head of the 9/11 commission and is an iconic figure in Garden State politics. While Tom Jr. is not his father, the name recognition gives him a significant leg up in any race.

"This is going to be a hotly contested race, if not a bare-knuckled brawl here because this is an important seat," says Doug Muzzio, a New Jersey political analyst. "The Republicans would love to take this seat."

The Democrats are just as determined to keep it, which is why political pundits are giving Mr. Corzine high marks for his apparent choice. They say that Menendez could help cement on the Democratic side the emerging Hispanic block in New Jersey, and that he could do this nationally, too. And there's his $4 million war chest, already stocked for the 2006 election.

"[Menendez] is certainly qualified, but he just is not yet known in New Jersey," says Ingrid Reed of the Eagleton Institute of Politics at Rutgers University in New Brunswick, N.J. "I think that a year in the Senate seat will provide him with the exposure he'll need to make a strong showing in the next election."

And in a state known for corrupt politics, local pundits say that Menendez appears to have passed another key test for New Jersey politicians - the "skeleton in the closet" test.

"He's a political leader in Hudson County, where everybody wears wires and everybody's under suspicion. It's part of the ethos of that part of New Jersey," says Mr. Muzzio, slightly tongue in cheek. "There were buzzes about political and personal stuff, and Corzine's people were aware of them and they did an extensive combing of the closet, and apparently Menendez came out clean."

• Diana Ransom contributed from New York.