WASHINGTON (AP) — Barack Obama rode a wave of voter passion in 2008 fed largely by intense dislike of President George W. Bush and the Iraq war, plus excitement among young and minority voters at the notion of electing the nation’s first black president.

Now, as Obama cranks up his re-election campaign, all those factors are absent.

The president has many tools, of course, for inspiring and exciting potential voters. But he faces a different landscape, one in which key supporters are disappointed by concessions he has made to Republicans, and discouraged by huge Democratic losses last fall.

Obama acknowledged the challenge last week in Boston. “Somebody asked me, how do we reinvigorate the population, the voter, after two very tough years?” he told Democratic donors. “How do we recapture that magic that got so many young people involved for the very first time in 2008?”

One answer, the president said, is to persuade hardcore liberals to swallow their anger over political compromises the administration reached with Republicans, even when Democrats controlled both chambers of Congress.

Obama’s concessions include dropping his proposed public option for health insurance, and extending Bush-era tax cuts for the wealthiest.

“There’s no weakness in us trying to reach out and seeing if we can find common ground,” the president said.

Despite his pleas, many Obama supporters clearly are disappointed. When he was inaugurated, 83 percent of Democrats said they expected his presidency to be above average, and nearly half predicted it would be “outstanding,” an AP-GfK poll found. Two years later, 68 percent of Democrats rated it above average so far, and just 20 percent called it outstanding.

Last fall’s elections were a disaster not only for the hundreds of Democrats voted out of Congress, governorships and state legislatures. They raised questions about Obama, too.

Thirty-seven percent of voters told exit pollsters they cast ballots explicitly to oppose the president, while 23 percent said their votes represented support for him.

Top Obama aides say things will look better by mid-2012, for several reasons.

They say GOP-led efforts to end state workers’ collective bargaining rights in Wisconsin and elsewhere are dramatically galvanizing the labor movement, a key Democratic constituency. Some union activists wish Obama would speak up more forcefully for them. But campaign aides say they think he is walking the right line by supporting unions without appearing unduly beholden to them.

Another key group, gays and lesbians, may shrug off several disappointments and work hard for Obama’s re-election because he signed legislation beginning the repeal of the Pentagon’s “don’t ask, don’t tell” policy, which barred gays from serving openly in the military.

Former White House press secretary Robert Gibbs said in an interview that the president will be able to show solid progress on the economy, education and other topics that will persuade dispirited Democrats to fight for Obama’s re-election.

These issues will “continue to animate core supporters of the president,” Gibbs said, and “get them passionately involved.”

He predicted that Republicans will help by focusing on undoing Obama initiatives, such as the 2010 health care overhaul, rather than offering an appealing alternative agenda. “Being against something is only going to get you so far,” Gibbs said.

Several Democratic activists acknowledged that some black voters are disappointed in Obama, wishing he would do more for impoverished Americans. But these voters might be far more outraged and energized, the activists say, by people who say the nation’s first black president was born in Kenya and has no legal right to be in the White House.

Some Democrats say they may need luck to replicate the passionate turnout of Obama’s first campaign. The often-stated claim that voters would embrace the health care law once it began taking effect has proven mostly untrue. But another year may change that, these Democrats say.

For now, the Obama team is unveiling few new ideas specifically keyed to firing up core constituencies. A recent White House conference call urged young voters to hold roundtables, which administration officials may attend, to discuss priorities and offer feedback.

Beyond that, Obama eventually plans large rallies similar to those in 2008. They create showy spectacles that excite young voters, but they also serve a fundraising role. People who enter the stadiums or buy Obama T-shirts are asked to provide their names and contact information, which are used later to request donations and volunteer activities.

Republicans predict Obama will easily exceed the record $750 million he raised for the 2008 race, even without a competitive Democratic primary.

When it comes to energizing the Democratic base and turning out the vote, however, Obama will sorely miss one person: George W. Bush. His unpopularity helped cripple GOP nominee John McCain’s efforts to overtake Obama in 2008.

A few days before the election, Bush’s disapproval rating hit a record 70 percent in the Pew Research Center survey. A declining number of likely voters, meanwhile, felt McCain would take the country in a different direction.

Whatever problems the eventual 2012 Republican nominee may have, Bush will be a distant memory. Obama will have to find a new punching bag, and new incentives, to fire up his base.

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Associated Press Deputy Director of Polling Jennifer Agiesta contributed to this report.