WASHINGTON - Four years ago, Senator Claire McCaskill was one of Barack Obama's biggest boosters in his presidential campaign.

But when he recently visited her state of Missouri, she did not have time to join him.

Many of McCaskill's fellow Democrats in Congress may also decide they are too busy to be with Obama, whose approval rating of about 40 percent as the economy struggles threatens to be a drag on their own reelection chances next year.

"You may see a number of Democrats say 'Sorry, I have a scheduling conflict,'" said a senior Democratic lawmaker.

Democrats face a big decision about whether to stand by their man in the November 2012 elections.

Many, particularly those in difficult campaigns like McCaskill, are tempted to keep their distance.

But others figure they can survive any anti-Obama backlash in their predominantly Democratic states. And they want to help their party's top star and fundraiser defeat whoever the Republicans throw at him.

More importantly, Democrats believe their best shot at retaining the Senate and taking back the House of Representatives is to help Obama rally and win a second term.

"If the president does well, we will do well," said Representative Jim McGovern of Massachusetts.

"I don't know what others will do but I say we need to run as a team," said Democratic Senator Sherrod Brown, facing a tough reelection race in Ohio. "Let's look ahead."

House Democrat Jim Moran of Virginia said: "The question is how vigorously we embrace him in terms of going the extra mile to get our people to knock on doors."

"I think we will. But the passionate idealism that we were gripped with when he was first elected has dissipated a little bit."

Some Democrats believe Obama has lost so much of his "hope and change" magic that they intend to stay away. That is particularly true if they are from a traditionally Republican or swing state, like West Virginia, hard hit by the weak economy that dogs Obama.

"In West Virginia, politics is not a team sport -- meaning hang on and do the best for yourself," said the state's first-term Democratic senator, Joe Manchin.

WILL DEMOCRATS DUCK OBAMA?

Unpopular presidents traditionally hurt their party in Congress.

Voter discontent with Democratic President Bill Clinton in 1994 and with Republican President George W. Bush in 2006 were key to their parties losing control of the House and Senate those years.

It's too early to know how many Democrats will duck Obama in 2012. But it could be at least a few dozen, analysts say.

The number may rise or fall in line with how his approval rating, now at 42 percent, and the US jobless rate, at 9.1 percent, move between now and Election Day.

A top Democratic aide, noting polls show most voters like Obama even though they do not approve of his job performance, said: "If his approval rating tops 50 percent and the economy improves, a lot of Democrats will want to be seen with the president."

But congressional Democrats are upset, even angry, with Obama right now.

They complain he has not consulted them, he moved toward the political right after Republicans won the House in the 2010 election and often has not distinguished between them and Republicans in blasting an even more unpopular Congress.

"There's a lot of resentment," one Democratic lawmaker said. "We are the ones who have put our necks on the line for him."

Ethan Siegal of The Washington Exchange, a private firm that tracks Washington for institutional investors, downplays tension between Obama and congressional Democrats.

"A political party is like a family. Some days you get along. Some days you don't. But you're still family," Siegal said. "The challenge for Obama is to gin up Democrats and get them to really want to go out there and campaign for him."

Back on Capitol Hill, Democrat McGovern said: "Every time I look at the Republican alternatives, my enthusiasm for Obama gets stronger and stronger and stronger. God Almighty, the Republicans are awful."

To the relief of Democrats, Obama recently got feistier. He took on Republicans with a populist $447 billion jobs package that he wants to fund largely with tax hikes on the rich.

Liberal Democrats want to see if he keeps fighting.

Dozens of Democrats, primarily House moderates, kept their distance from Obama in the 2010 election dominated by a near double-digit jobless rate. But most lost anyway in a Republican tidal wave aided by the Tea Party movement.

There are now about two dozen moderate Democrats left in the House. Most are expected to stay away from Obama next year. Currently, a half dozen or so of what will be 33 Senate Democratic nominees are likely to campaign without Obama.

McCaskill was an early backer of Obama in 2008. Yet with her state seen as leaning Republican, she stayed in Washington when Obama made a campaign visit to Missouri on Oct. 4.

Republicans ran an ad mocking McCaskill for declining to join the president. The spot showed her endorsing him with the words "Our economy needs Barack Obama as president."

McCaskill said she could not go back to Missouri because of a scheduling conflict and dismissed criticism as unfounded.

"People making a big deal of this is silly," McCaskill said. "They don't know me very well if they think I'm going to run away from the president. I'm not."

One of her Democratic colleagues sounded skeptical.

"If Obama's approval rating was at 70 percent, she would have been there in a heartbeat," the lawmaker said.