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 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.

There are now 101 vacancies among the nation's 857 district and circuit judgeships, with 46 classified as judicial emergencies in which courts are struggling to keep up with the workload. At least 15 more vacancies are expected this year, according to the Administrative Office of the U.S. Courts. When Obama took office in 2009, 54 judgeships were open.

Most of the departing judges have taken what is known as senior status - semi-retirement in which they receive full pay but can take a reduced workload and are not considered active members of the court. But court officials say the increased work, heavier caseloads and lack of pay increases are prompting more judges to leave the bench entirely.

The effect is most visible in civil cases, with delays of up to three years in resolving discrimination claims, corporate disputes and other lawsuits.

"Ultimately, I think people will lose faith in the rule of law,'' said Alex Kozinski, chief judge of the U.S. Court of Appeals for the 9th Circuit in California. "We as a nation believe that if you have a dispute, you go to court and within a reasonable period of time, you get a decision.''

Kozinski, who oversees the federal court in the Commonwealth of the Northern Mariana Islands, a U.S. territory, said the government has spent at least $250,000 to fly visiting judges to the island of Saipan, where the sole judge retired last year.

In Arizona, the number of criminal cases has increased 65 percent since 2008, while three of the 13 federal judgeships are vacant. Former chief judge John M. Roll was working on the judicial emergency declaration when he was killed during last month's shootings in Tucson.

Beyond the practical need for judges, the political stakes are high. The vast majority of federal cases are dispensed through the district and circuit courts of appeal, with the Supreme Court hearing fewer than 100 cases each year.

And control of the influential appellate courts tends to shift with the party in power: By the time Bush left office, his appointees had given Republican nominees a majority of about 56 percent on those bodies.

Party affiliation is not a perfect predictor of a judge's behavior, but studies have shown that Democratic and Republican nominees vote differently on some ideologically charged issues, such as abortion, gay rights and capital punishment.

When Obama took office, experts predicted he would flip the Republican appellate court majority in his first term. But in 2009 and 2010, the administration nominated 103 district and circuit judges, compared with 129 during Bush's first two years and 140 in President Bill Clinton's first two years, said Russell Wheeler, a Brookings Institution scholar who studies federal courts.

White House counsel Robert F. Bauer attributed the slow start to the administration's large legislative agenda, two time-consuming Supreme Court vacancies and an increasingly complicated background review process for nominees.

"We have made progress,'' Bauer added, pointing out that the pace of nominees picked up significantly last year. But those nominees faced a tough road in the Senate, as Republicans repeatedly exercised their right to "hold over" nominees before sending them to the floor.

The 60 nominees confirmed in Obama's first two years in office made up the lowest number in 35 years, according to the Senate Judiciary Committee.

Still, Obama has been putting his stamp on the courts. When he took office, Democratic appointees had small majorities on two appeals courts - the New York-based 2nd Circuit and the 9th Circuit. Obama's nominees have also given Democrats control of the 4th Circuit and the 3rd Circuit, which covers Pennsylvania, New Jersey and Delaware.

The 4th Circuit is an influential voice on national security and one of the appellate courts expected to hear challenges to the health-care overhaul law. It has a 9 to 5 Democratic majority, because of four Obama appointees.

"That's almost unimaginable,'' said Curt Levey, executive director of the conservative Committee for Justice. "When I first went to law school, that was the one circuit you knew was conservative.''

If the Senate approves the 48 pending White House judicial nominations, the circuits would be about evenly divided between Democratic and Republican nominees, according to Wheeler's analysis. "This Congress has the power to shift the balance rather substantially,'' he said.

Saying the courts face "a severe problem,'' Bauer vowed that the White House will move nominees "at a very steady clip. . . . We will use all the resources at our disposal to bring attention to the issue and work on a bipartisan basis.''

Senate Majority Leader Harry M. Reid (D-Nev.) and Minority Leader Mitch McConnell (R-Ky.) struck a "gentleman's agreement" in January to quash many of the procedural tactics that have slowed nominations.

"We'll be discussing with Senator Reid how to begin moving them in an orderly fashion,'' said Don Stewart, a spokesman for McConnell.

Liberal groups, which have blasted what they call Republican obstructionism and pushed the White House to focus more on judges, said this year will be key.

"This is really a critical time for the legacy this president will be able to create on the federal judiciary,'' said Marge Baker, an expert on judicial selection at People for the American Way. "We have an opportunity now, and we have to take advantage of it.''

markonj@washpost.com murrays@washpost.com

Research editor Alice Crites contributed to this report.