TRENTON, N.J. (AP) — Gov. Chris Christie is perhaps the nation's highest-profile Republican — but that's no guarantee the seat held by the late Sen. Frank Lautenberg will switch to GOP hands. In fact, it's that profile that could help preserve the seat for the Democrats, political observers say.

Christie has two key decisions: Whom to appoint to fill the seat in the short term, and when to let voters have their say on who will fill it until the term expires in January 2015. There are layers of political calculations involved, along with possible legal complications.

Christie, widely considered a possible presidential candidate for 2016, needs to decide whether to appoint someone who will merely keep the seat warm — or someone who will seek to keep it in the 2014 election. He also needs to decide whether a Democrat or a Republican is best suited for the seat.

With Lautenberg's death, the Senate now has 52 Democrats, 45 Republicans and two independents who caucus with the Democrats. Along with their perpetual federal budget battles, senators are now starting to address changes in immigration policy.

New Jersey has not elected a Republican to the Senate since 1972. And it hasn't had one serve there at all since 1982, when Republican Gov. Tom Kean appointed Republican Nicholas Brady to finish the term of Democrat Harrison Williams, who resigned amid scandal in the last year of his term. Lautenberg won the seat later that year and remained in the Senate until his death, except for a brief retirement in 2001 and 2002.

If Christie picks a Democrat, it may not play well with Republican presidential primary voters, who could see him as disloyal to his party. But if he picks a Republican, he risks upsetting voters who chose a Democrat for the seat, and a moderate Republican may not help him much with that group, either.

No one has yet begun campaigning for the job publicly.

Political analysts say the list of Republican possibilities includes state Sen. Tom Kean Jr.; U.S. Rep. Chris Smith; former Gov. Christie Whitman; state Sen. Joe Kyrillos, who ran for the U.S. Senate last year; state Sen. Kevin O'Toole; or Bill Baroni, the deputy executive director of the Port Authority of New York and New Jersey.

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Another possibility could be Lt. Gov. Kim Guadagno, which would open a spot on Christie's re-election bid ticket this fall for another Republican.

Despite the risks, Christie could consider appointing Newark Mayor Cory Booker, a Democrat who announced earlier this year plans to run for Lautenberg's seat in 2014, said Brigid Harrison, a political scientist at Montclair State University. The move could backfire, she said, but it would help Christie's image with New Jersey Democrats and African-Americans across the country — especially since history shows it's hard for a Republican to win a Senate seat in New Jersey.

"For his own political future, it is not a bad gamble" for Christie, Harrison said.

Another major question is the timing of the election.

Frank Askin, a professor at the Rutgers-Newark School of Law, said there are two conflicting state laws about when an election to fill the seat may be held. Options include this November, when the governor is also on the ballot; November 2014; or a special primary and general election some other time over the next 19 months at a cost of millions of dollars.

State Senate President Stephen Sweeney, a Democrat, said Christie should appoint a Democrat, because the seat was held by an elected one, and then hold a special election this November. But he said he thinks Christie may be reluctant to appoint a Democrat and hesitant to give up his place at the top of this fall's ballot.

Askin said he expects Democrats to sue to try to force an election this year if Christie does not do that on his own.

The main timing question Christie will consider if he chooses a Republican is whether being on the ballot with the popular governor might help that candidate win a race, said Matthew Hale, a political scientist at Seton Hall University.

"Does he think that there's anybody out there who can run and beat Booker?" Hale asked. "If there is, put that person in, give them a chance to run and have a shot."

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Mulvihill reported from Haddonfield.