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Republicans' big midterm wins throw a potential curveball at President Obama as he weighs his replacement for outgoing Attorney General Eric Holder -- forcing him to decide whether to introduce a nominee during the lame-duck session or take his chances with a more hostile Senate majority after January.

A short list of contenders already is making the media rounds. But perhaps the more pressing question is when Obama will make his move. With Republicans winning the Senate majority, Obama could have a tougher time if he waits until next year to nominate someone.

However, he also could inflame tensions by pressing ahead in a lame-duck session -- at a time when both sides claim to be giving cooperation a shot.

Hans von Spakovsky, senior legal analyst at Heritage Foundation, suggested the timing might depend on whether Obama pushes someone with political baggage.

"I think if he has someone in mind who might be at all controversial, he won't have any trouble getting [Democratic Senate Majority Leader] Harry Reid to push it through the lame-duck session," he said.

So far, missing from the apparent short list are some of the more colorful and familiar names who surfaced in the wake of Holder's resignation announcement -- like outgoing Massachusetts Gov. Deval Patrick and Manhattan U.S. Attorney Preet Bharara. The three reported to be in the running, according to unnamed White House sources: Brooklyn U.S. Attorney Loretta Lynch, U.S. Solicitor General Donald Verrilli, and current Labor Secretary Thomas Perez.

Last week, Holder, who announced his departure in September, told a reporter that he expects to stay on until early February. Prior reports, though, signaled the White House might try and replace him shortly after the election.

“I don’t know if there are any [nominees] that Republicans would speedily or readily confirm,” said Sarah Binder, congressional expert at the Brookings Institution, who believes the two-month lame duck session may be too crowded with budget and spending priorities to properly vet and channel a nominee through the dangerous shoals of a Senate confirmation.

So it’s possible, she said, that these restraints will lead to “the White House saying we’ll just have to find a nominee come January, and that it will be a hard road but we’ll find a nominee who will be a bit more acceptable to Republicans.”

That might not include Perez, a former assistant attorney general at DOJ, who was opposed by Republicans when he was confirmed as Labor Secretary in a party line vote on July 18, 2013. He was called a “crusading ideologue” by Sen. Mitch McConnell, R-Ky., who is poised to take over Reid’s position in January. Sen. Ted Cruz, R-Texas, a judiciary committee member who voted against Perez, said the nominee showed “a lack of respect for the rule of law.” Critics pointed to his work on voting rights and immigration as “radical.”

Meanwhile, Lynch is being called an under-the-radar contender for Holder’s job. She is a 55-year-old Harvard grad with no particular ties to Obama – which could either help or hurt her in the process. She is close to Holder, however, serving on his AG’s Advisory Committee in Washington.

During her tenure as U.S. Attorney, she convicted potential terrorists in a thwarted Al Qaeda attack on New York subways, and a Mexican drug kingpin, and she brought tax evasion charges against Republican Rep. Michael Grimm.

In addition, seeing Lynch become the first African-American woman to hold the AG position would “be inspiring to millions of people, especially children, to know what they could become,” said former federal prosecutor Andrew Weisman, who worked closely with Lynch.

As solicitor general, Verrilli has the confidence of the president, but like Perez, might have some difficulties getting past Senate critics. Republicans don’t like the fact that he is the administration’s top lawyer on every issue they have fought against at the Supreme Court level, including the Affordable Health Care Act. Others say he has a mixed record on winning cases.

Other names also have been floated. The National Fraternal Order of Police (FOP) has asked the president to nominate the number two at the Department of Homeland Security, Alejandro Mayorkas, for the job.

In a letter to Obama dated Oct. 31, FOP president Chuck Canterbury wrote that his “reverence for the law, his respect for people of all persuasions and backgrounds and ready willingness to give a fair hearing to opposing views make him an extraordinary candidate.”

Whoever the nominee is, he or she will have to face Holder’s baggage with Senate Republicans, which will no doubt include questions on the ongoing IRS scandal, and any executive orders the president issues to protect undocumented workers in the U.S. from deportation. “Anyone who is not cooperative and who is not willing to answer questions is going to have a hard time,” said von Spakovsky.

That means the nominee will not only have to fulfill the myriad requirements of the job, but be able to keep his or her cool under fire in the hearing room.

“They will need to know their way around Capitol Hill, in congressional offices and in hearing rooms, and be able to work with both sides of the aisle," said Michele Jawanda, legal expert at the Center for American Progress. "The attorney general operates under the spotlight, which is why the position requires a savvy and calm, but an aggressive pursuer of injustice anywhere.”

The Associated Press contributed to this report.