But the challenges to getting an enthusiastic turnout for Democrats in 2010 are huge. Young voters and left-wing Democrats have become frustrated with progress on the Obama agenda in Washington. Polls show that Obama’s popularity among younger Americans is down.

“People are rightfully disenchanted’’ with the way things are going in Washington, said Michael Vastola, 21, a Tufts University senior and active College Democrat. “I’m personally concerned, because I hope they keep their interest in this upcoming election.’’

While many young voters imagined that an Obama presidency would mean a speedy closure of Guantanamo Bay prison, a wind-down of the wars in Iraq and Afghanistan and a health care plan that would, at least, provide a government insurance plan to compete with the private sector, they instead are frustrated at the slow pace of change, Vastola and others said.

“There was this expectation that this was going to be like a Hollywood movie. He was a candidate almost fictionalized from day one,’’ Boston-based Democratic political consultant Michael Goldman said of Obama. “Does it make me frustrated? It does. But it’s reality, it’s the world as it really is, not the fantasy.’’

The trend threatens to do serious damage to the Democrats this fall as they seek to hang onto their majorities in Congress. With “tea party’’ activists and other conservatives eager to vent their anger over Democratic policies, low Democratic turnout could be devastating to the majority party. While a GOP takeover of either chamber of Congress seemed highly unlikely even a month ago, Democratic officials, spooked by developments in deep-blue Massachusetts, fear that Republicans could score big upsets this fall.

The White House is clearly disheartened by the attacks it is getting from the left flank of the party.

“I don’t know why some segments of political observers don’t seem to be as motivated. There’s a lot at stake. There’s a lot at stake in the election in Massachusetts; there’s a lot at stake in what’s debated every day on Capitol Hill. What’s at stake is whether we’re going to go forward with ideas for an economic recovery,’’ said White House press secretary Robert Gibbs.

Continued...