Federal judges have been retiring at a rate of one per week this year, driving up vacancies that have nearly doubled since President Obama took office. The departures are increasing workloads dramatically and delaying trials in some of the nation's federal courts.

The crisis is most acute along the southwestern border, where immigration and drug cases have overwhelmed court officials. Arizona recently declared a judicial emergency, extending the deadline to put defendants on trial. The three judges in Tucson, the site of last month's shooting rampage, are handling about 1,200 criminal cases apiece.

"It's a dire situation," said Roslyn O. Silver, the state's chief judge.

In central Illinois, three of the four judgeships remain vacant after two of President Obama's nominees did not get a vote on the Senate floor.

Chief Judge Michael McCuskey said he is commuting 90 miles between Urbana and Springfield and relying on two 81-year-old "senior" judges to fill the gap. "I had a heart attack six years ago, and my cardiologist told me recently, 'You need to reduce your stress,' '' he said. "I told him only the U.S. Senate can reduce my stress.''

Since Obama took office, federal judicial vacancies have risen steadily as dozens of judges have left without being replaced by the president's nominees. Experts blame Republican delaying tactics, slow White House nominations and a dysfunctional Senate confirmation system. Six judges have retired in the past six weeks alone.

Senate Republicans and the White House are vowing to work together to set aside the divisions that have slowed confirmations, and the Senate on Monday approved Obama nominees for judgeships in Arkansas, Oregon and Texas. Eight more nominees are expected to receive votes in the coming weeks.

If the backlog eases, Obama will have the chance to appoint dozens of judges who might gradually reverse what many consider a conservative drift in the lower federal courts under the George W. Bush administration.

Even with Obama's difficulties in the past two years, his appointees have given Democrats control of two of the nation's 13 federal circuits, including the influential U.S. Court of Appeals for the 4th Circuit in Richmond, long a conservative bastion.

And about three-fourths of his appointees have been women or minorities, a historically high rate aimed at diversifying a judiciary that is made up of nearly 60 percent white men.

"It's fair to say that the Obama administration has had an impact on the federal courts and that at the end of this Congress, I believe that impact will be reinforced,'' said Sheldon Goldman, an expert on judicial selection at the University of Massachusetts at Amherst.

Obama's opportunity is brief, however, because the presidential election season will ramp up by next year. And even with the current promises of bipartisanship, Senate rules allow individual senators to hold up nominations.