The beginnings of presidential second terms usually bring major personnel changes. For President Barack Obama, the shuffling in top positions comes as his administration grapples with averting a major year-end financial crisis.

Time is ticking down on a “fiscal cliff” of mandatory spending cuts and tax increases. Congress and the White House have a Dec. 31 deadline for reaching a deal. Economists say going over the “cliff” could mean another recession, but so far there’s been no sign of a comprehensive agreement, and attention is starting to turn to finding an emergency short-term fix.

Obama also faces another cliff — looming vacancies at the top of both his national security and economic teams.

U.N. Ambassador Susan Rice’s sudden withdrawal from consideration to be Hillary Rodham Clinton’s successor as secretary of state sidesteps a bruising confirmation battle in the Senate and removes a major source of tension with congressional Republicans.

But Obama still has lots of work to do.

With Rice now out of the picture, a leading contender for the top diplomatic post is John Kerry, chairman of the Senate Foreign Relations Committee. Kerry could probably win easy confirmation by his Senate colleagues, but his nomination could jeopardize a now-safe Democratic Senate seat in Massachusetts.

Defense Secretary Leon Panetta also wants out. Chuck Hagel, a former Republican senator from Nebraska, has emerged as the front-runner for the Pentagon job.

Meanwhile, Obama has already lost most of his original economic team and Treasury Secretary Timothy Geithner says he’s ready to leave, too — hopefully sometime next month.

The secretaries of State, Defense and Treasury are the top jobs in any administration. And Obama must fill them, along with dealing with a serious economic crisis, at roughly the same time.

___

Follow Tom Raum on Twitter: http://www.twitter.com/tomraum