As Congress returns from its August recess today, Republicans face a far more troubling political landscape than the one they left a month ago, according to lawmakers in both parties.

Gasoline prices have skyrocketed, the Bush administration is being widely criticized for its handling of Hurricane Katrina, and as the war in Iraq grows increasingly unpopular, the president's approval ratings have sunk to an all-time low. Further complicating the picture is a rare double vacancy on the Supreme Court, which could trigger sniping between the GOP's center and right wing if not deftly handled.

"We're going to have a busy time," said Senate Majority Leader Bill Frist (R-Tenn.).

As the pressure on Republicans builds, Democrats are sounding emboldened. One sign of GOP unease: The Senate was supposed to vote this week on whether to permanently repeal the estate tax, but Frist said yesterday that the bill will be temporarily shelved. The announcement came two hours after Senate Minority Leader Harry M. Reid (D-Nev.) called for Republicans to back off tax cuts in the wake of the Katrina tragedy. "Not now, for heaven's sake," Reid said.

Some conservatives worry that Bush has given Democrats an opening by naming John G. Roberts Jr. to succeed Chief Justice William H. Rehnquist, who died Saturday night. Roberts had been nominated to succeed the retiring Sandra Day O'Connor, and that confirmation process was scheduled to start today. Because Rehnquist was a solid conservative and O'Connor a centrist, the argument goes, liberals will fight much harder to keep a conservative -- such as Roberts -- from getting the O'Connor seat, whereas the philosophy of Rehnquist's successor is less vital to them.

Lawmakers in both parties said the surging price of gas and spot shortages are leading concerns in their states and districts, and Democrats will try to get the upper hand by calling for price caps and a requirement that oil companies and refineries disclose their pricing policies. Frist said Republicans would proceed with legislation to allow oil drilling in the Alaska wilderness.

Another immediate concern will be disaster relief. Frist, a surgeon who spent the weekend treating hurricane victims in New Orleans, said the Senate would focus on several Katrina-related matters, including aid to victims, rebuilding and economic development assistance, and examining the many ways that government fell short in dealing with the crisis. "We're going to take a hard, hard look at our disaster response," Frist said.

Although congressional Republicans facing reelection next year are unhappy with Bush's slide in the polls, there's no sense of panic, said Stu Rothenberg, who writes an independent political newsletter. "But inevitably, if we continue to see a softening in the president's numbers, every Republican is going to be expressing some concern, if not alarm," he said.

The biggest wild card, Republicans say, is the war in Iraq. The dominant issue before the hurricane will resurface when Congress tries to complete a defense bill.

"People don't see light at the end of the tunnel in Iraq," said Sen. Charles E. Grassley (R-Iowa). "If the situation a year from now is the same, it's going to be the number one issue in the next election, and consequently for incumbent Republicans, a problem."

One of the more vulnerable GOP members is Rep. Michael G. Fitzpatrick, a freshman from a moderate district in the Philadelphia suburbs. Fitzpatrick does not air his concerns publicly, as a few Republicans are beginning to do, but he is worried about the safety of U.S. troops and has written to the Pentagon pressing for improved body armor and vehicle protection.

"I think everyone is on the edge of their seat right now, hoping for the best, but preparing for what comes next," Fitzpatrick said. If the situation does not improve soon, "I think you will see more members of Congress speaking up generally," he said.

Katrina could have bolstered Bush's standing, but instead his response may have weakened his standing in Congress, particularly among lawmakers from the affected Gulf Coast region. Sen. Mary Landrieu of Louisiana, a conservative Democrat who often supported Bush proposals, was outraged to hear White House officials disparage the local response. On ABC's "This Week," she said of Bush, "One more word about it after this show airs and I might likely have to punch him. Literally."

Sen. Trent Lott (R) of Mississippi, who lost his Pascagoula home in the storm, released a statement headlined "I Am Demanding Help for Mississippi." After a blistering critique of the Federal Emergency Management Agency, Lott thanked Bush for his efforts.

Some argue that the hurricane disaster, high fuel prices and continued problems in Iraq will increase chances that Bush will name a centrist, consensus nominee to replace O'Connor.

Even before Katrina hit, Republicans were struggling to keep their agenda on track. They had made little progress with revamping Social Security, but immigration reform was gaining momentum.

Bush and congressional Republicans might argue that soaring gasoline prices and a storm-damaged economy call for tax cuts -- in the name of helping middle-class people fuel their cars and keeping Katrina from slowing the economy, Rothenberg said. House Majority Whip Roy Blunt (R-Mo.) said last week that Congress should consider tax cuts as part of a "stimulus package" in response to Katrina.

But Democrats say they are poised to pounce. "If they think they can go forward as if nothing's changed, they do not understand what the rest of America has witnessed over the past week," said Rep. Rahm Emanuel (D-Ill.), who heads the House Democrats' campaign committee.