WASHINGTON – When a Senate committee opens hearings today on what the government did wrong in response to Hurricane Katrina, there will be a conspicuous absence at the witness table: No one who actually handled the disaster will be there.

Hesitant to interfere with ongoing relief operations in the storm-ravaged South, lawmakers in Washington will be left to grill veterans of past disasters. That is an emblem of how hard it is for Congress to grapple with the calamity that has washed away much of the rest of its legislative agenda.

The hurricane is testing Congress’s ability to do something that the lumbering institution is not well-equipped to do: move quickly and decisively on a huge, bipartisan project.

In their early response, members of Congress instead have been doing what seems to come more naturally: Spending lots of money, hurling partisan insults, and holding hearings – even if the most pertinent witnesses cannot attend.

Senate Budget Committee Chairman Judd Gregg, a Republican of New Hampshire, has decried the lack of focus in Congress’s response so far and has called on GOP leaders and the White House to do more to set priorities among the ideas, bills, and hearings flowing through the Capitol.

“I have been extremely concerned about this, because I think we are going to wake up six months from now or three months from now and realize that a haphazard approach has not been effective either in resolving the problems in the Gulf Coast or in managing the taxpayers’ money effectively,” Mr. Gregg said in a speech Monday on the Senate floor.

Sharing those concerns, Senator Domenici, a Republican of New Mexico, has prepared a letter to President Bush urging him to put a “coordinator” in charge of overseeing spending on the recovery effort. “Who’s going to manage and help Congress decide what to fund?” he asked in an interview. “Conventional approaches are going to cause total chaos. If we leave it up to committees, if we leave it up to individual claimants telling us what they need, we’re in for a real mess.”

Republican leaders have tried to coordinate plans for investigating what went wrong in the government’s hurricane response by proposing a joint House-Senate committee. But even that has not gotten off the ground, because Democrats have objected that it would be stacked in favor of Republicans and prone to cover up rather than investigate the Bush administration’s mistakes.

Senior GOP aides and administration staffers began meeting last week to plan longer-term policy for rebuilding the damaged region. But that has not stopped lawmakers from offering their own ideas in the meantime.

“It’s hard to be patient when you are flat on your back,” Senator Lott, a Republican of Mississippi, said. “But we’ve also got to make sure our leadership pulls us together to coordinate our efforts.”

The situation underscores how thoroughly the Katrina aftermath has challenged and changed Congress’s rhythms. Republicans who run Congress, not usually inclined to draft grand government designs, are being asked to consider new aid to thousands of displaced people. Two political parties so polarized that they can hardly agree on the time of day are being asked to come together to rebuild a city.

The short- and long-term policy questions that now dominate are a far cry from Congress’s more routine ideological issues, such as abortion and Social Security, where lawmakers tend to hew to party lines.

“They are not used to serious oversight or real deliberation,” an expert on Congress at the Brookings Institution, Thomas Mann, said. “It’s all, ‘Are you with the president or against him?'”

For members of Congress representing the devastated area, the debate is immediate and personal. In a bipartisan House-Senate enterprise, lawmakers from the area are compiling a wish list of what aid their states need.

At least nine committees and subcommittees have planned hearings this week on Katrina-related subjects, including the effectiveness of hurricane forecasting, housing programs for hurricane victims, and the role of private charities. The broadest inquiries into the government response are being held today by the Senate Homeland Security and Governmental Affairs Committee and tomorrow by the companion House panel. But those committees’ chairmen said they would not call any of the front-line officials of FEMA or state and local agencies to testify, at least for now, because that would detract from ongoing relief efforts.

Instead, the Senate panel will hear from officials with experience handling major disasters, including a former governor of California, Pete Wilson, who was in office during the 1994 Northridge earthquake. Lawmakers will ask for advice about what initial aid the government should provide in the wake of the hurricane.