WASHINGTON — Congress returns to Washington on Monday with a full slate of must-do legislation, just three short weeks before the Christmas recess and with four members of the slim Democratic Senate majority likely to miss votes as they campaign for president.

The lawmakers' to-do list would be daunting under the best of circumstances: a major energy bill, legislation to rein in President Bush's warrantless wiretapping program, 11 of the 12 annual bills to fund the federal government, a farm bill and a bill to stave off the expansion of the alternative minimum tax and extend a raft of expiring tax credits.

"Members are coming back to a lot of unfinished business," Bush said Saturday in his weekly radio address. "The clock will be ticking because they have only a few weeks to get their work done before leaving again for Christmas."

Senate Majority Leader Harry Reid, D-Nev., must tackle that agenda and battle a combative GOP minority and an intransigent Republican president without a reliable majority.

"The majority leader's job is always tough, and his job has been made all the more difficult by the presidential candidates," said Senate Minority Whip Trent Lott, R-Miss., who will resign by month's end. "But if you're going to run for president, you've got to get out there and run for president."

Senate Democrats normally can count on a 51 to 49 majority, assuming independent Sen. Joe Lieberman of Connecticut stays with his old party. With Sens. Hillary Rodham Clinton, D-N.Y., Barack Obama, D-Ill., Joe Biden Jr., D-Del., Christopher Dodd, D-Conn., and John McCain, R-Ariz., campaigning furiously for party presidential nominations, Republicans can have an effective 48 to 47 majority, with an extra vote from Lieberman on most national security issues.

With the Iowa caucuses just one month away, many of those candidates have warned their leadership not to expect them around much. Sen. Richard Durbin, D-Ill., the Senate chamber's second-ranking Democrat, who is in charge of vote counting, said he does not expect to see the candidates during debates but hopes to schedule votes that allow senators enough time to return to Washington.

The House this week hopes to finish an energy bill that would raise automobile fuel economy standards for the first time in 32 years, then hand it off to the Senate for final passage the following week.

With the presidential campaign in full swing, how the Senate will handle any moderately controversial legislation is a mystery — even to Democratic leaders. "As the Democratic whip, I'm making a list and checking it twice," Durbin said.

In the Senate, where schedules are famously unreliable, leaders have to jump at any opportunity to hold final votes. On Nov. 8, at 11 p.m., when such a window opened suddenly to confirm Michael Mukasey as attorney general, not one of the five presidential candidates was on hand to vote.

Earlier in the day, all five also missed the first veto override of the Bush presidency, when Congress salvaged a water projects law. And only Biden was on hand the week before for final passage of a bill expanding the State Children's Health Insurance Program.

"They understand they might have to drop what they're doing and fly in for a vote," Durbin said. He noted that the Democratic candidates hopped a red-eye flight after the Nov. 15 debate in Nevada to make a 9 a.m. vote on Iraq war funding. Clinton then turned around and flew to the West Coast.

Even before the sprint to the Iowa caucuses, the senator-candidates have been increasingly absent from the chamber. McCain has missed more than 53 percent of roll call votes this year and has not cast a single vote since Oct. 24. Biden, Dodd and Obama have missed more than a third of all votes this year, according to washingtonpost.com's congressional database. Clinton has missed just 18 percent of votes, but was on hand for only three days of voting in the month leading up to the Thanksgiving recess.

Dodd has vowed to be in Washington when the Senate takes up wiretapping legislation — because he has promised to filibuster any version that offers telecommunications companies retroactive immunity from lawsuits for supplying the administration with telephone and e-mail records.

But his staff has expressed hope that the issue will not come up until January. By then, Dodd's long-shot campaign may have been derailed and he would once again be a full-time senator.

On the spending measures, Republicans privately acknowledge a deal could be cut that would allow some level of additional spending on domestic priorities for Democrats — who currently have set the measures at $11 billion above Bush's request. To achieve that, however, they must provide the administration $50 billion in "bridge" funds for the Iraq war without any timelines for the withdrawal of troops attached.

But Reid and House Speaker Nancy Pelosi, D-Calif., have adamantly said no such war funding will pass without a timeline for withdrawal of combat forces by the end of 2008.

Contributing: Associated Press