Gov. Chris Christie on Tuesday set an October special election to fill the U.S. Senate seat made vacant by Frank Lautenberg’s death, a decision that gets voters the quickest possible say on who will represent them in Washington but preserves Christie as the top attraction on November’s ballot.

The move means the state will have two statewide elections three weeks apart, a rare occurrence that’s already drawing criticism.

At a news conference, Christie didn’t answer the big question of whom he’ll appoint to fill the seat in the meantime, but he said he has a list of possibilities in his head and will announce a decision quickly.

The Republican governor said he’s not obligated to nominate someone in line philosophically with the liberal Lautenberg. Christie plans to have the temporary representative in place when the Senate begins debating immigration reform next week.

Christie easily won the Republican nomination for governor Tuesday in his bid for a second term. He defeated Atlantic County conservative Seth Grossman, setting up a match against state Democratic Sen. Barbara Buono in the Nov. 5 general election. Buono won the Democratic nomination for governor on Tuesday.

Christie’s move to hold a special election only weeks before the statewide November election generated criticism from Democrats, who said it was a waste of money and politically motivated. Christie said the state will pick up the $24 million tab.

“The people need to have a voice and choice,” Christie said. In opting for a primary rather than letting each party’s political committees select nominees, he said he didn’t want “insiders and a few party elites to determine who the nominee of the Republican party and the Democratic party will be.”

The Senate primaries will be held Aug. 13 and general balloting on Oct. 16. The winner of the special election will serve until Lautenberg’s term expires in January 2015.

Behind the scenes, Republicans had pushed for Christie to appoint a Republican and put off the Senate election until November 2014 to give the GOP appointee time to build a following among voters. The state’s Republicans have not elected a member of their party to the Senate since 1972 and Newark Mayor Cory Booker, the favorite to win the Democratic nomination, expects to mount a formidable campaign in the Democratic-leaning state.

Assembly Speaker Sheila Oliver, a Democrat, said Christie chose the October date so that Democratic voter turnout for the Senate election doesn’t threaten his re-election bid.

“The November general election date is what’s best for taxpayers and voter turnout,” Oliver said. “It’s unquestionably the best option, but Gov. Christie has chosen to put partisan politics and his self-interest first.”

There’s nothing in the law that would have stopped Christie from holding the Senate election on Nov. 5, the same day as the general election, said Frank Askin, director of the Constitutional Rights Clinic at the Rutgers-Newark School of Law.

“It seems to me the option he chose was the only one that guarantees he will not be in an election with Cory Booker running on the Democratic line,” Askin said.

Booker, a popular Democrat, could drive black voters to the polls who might not otherwise be inclined to turn out for Buono. He announced months ago that he was planning to seek the Senate seat in 2014. U.S. Rep. Frank Pallone has also expressed interest.

Lautenberg, who turned 89 in January and was the oldest member of the Senate, at first bristled at Booker’s candidacy. But the Democratic lawmaker, who was first elected to the Senate in 1982, announced in February that he would not seek re-election next year and would retire when his term expired at the beginning of 2015.

Lautenberg died after suffering complications from pneumonia. A funeral is scheduled for today.