WHY, asks a Democrat leading a training session for fellow activists, doesn't “Yes we can” work as a slogan any more? “Because we haven't,” a jaded participant responds. Progressives, as bedrock Democrats like to call themselves, are despondent. The election euphoria of 2008, when their party secured heavy majorities in both chambers of Congress and Barack Obama won the presidency with ease, has deflated so rapidly that analysts are now diagnosing on the left an affliction they ascribed to the Republicans back then: an “enthusiasm gap”.

The present gap is really more of a chasm. Gallup, a pollster, reckons that a mere 28% of Democrats are “very enthusiastic” about voting, compared to 44% of Republicans. By the same token the Pew Research Centre found in June that only 37% of liberal Democrats were “more enthusiastic than usual” about going to the polls, compared with 59% of conservative Republicans. And according to an NBC/Wall Street Journal poll the same month, the categories of voters whose interest in elections has dimmed the most since the last one are liberals and those who voted for Mr Obama (see chart). “You can't deny the level of disappointment,” says Raul Grijalva, a Democratic representative from Arizona and head of the Congressional Progressive Caucus.

Mr Obama and the Democrats' leaders in Congress insist that progressives have a lot to be thankful for: the passage this year of universal health care, the fondest of liberal ambitions for decades; a financial-reform act that increases oversight of the wayward bankers who, in the minds of many, were bailed out at humbler workers' expense; the extension of unemployment benefits in the teeth of vociferous Republican objections, and so on. But doctrinaire Democrats can find fault with all these achievements. Mr Obama's health-care reform, for example, does not involve a state-owned insurer (“the public option”) designed to keep the private ones honest, as many on the left had wanted. The extension of unemployment benefits was merely the rump of a much more ambitious proposal for a second stimulus package, most of which fell by the wayside. And the scalding of Wall Street's fat-cats has not gone nearly far enough for many Democrats' taste.

Worse, Mr Obama's administration has not made much progress at all towards several cherished leftish goals. The president claims to support replacing secret ballots with public recruitment drives to make it easier for workplaces to unionise (an idea known as “card check”), but the proposal has stalled in Congress. Mr Obama's oft-professed goal of capping America's emissions of greenhouse gases has come to naught, as has his talk of comprehensive immigration reform.

Perhaps most galling to many Democratic activists, the party's leaders often seem more concerned about pandering to their critics on the right than looking after their devoted supporters. How else, many ask, could you explain the government's unseemly haste to dismiss Shirley Sherrod, a civil servant falsely accused of racism by a right-wing blogger? Why else would it take so long for legislation to allow gay soldiers to serve openly in the army to limp through Congress?

The White House complains that the left is making the best the enemy of the good. In a recent interview with the Hill, a newspaper that focuses on Congress, Robert Gibbs, the president's press secretary, lamented that nothing Mr Obama did would ever be good enough for some on the left. As for those who thought the president was like George Bush, “they ought to be drug-tested,” fumed Mr Gibbs.

The Democrats' top brass blame the party's failings on Republican obduracy and trickery. Harry Reid, the party's leader in the Senate, complains, not without reason, that blocking legislation by filibuster has become a Republican reflex. But many progressives see this as a feeble excuse: “I'm sick and tired of hearing we don't have 60 votes. Go get them!” thundered Ed Schultz, a bombastic liberal radio host, at a recent progressive powwow, to equally thunderous applause.

The disillusionment of the Democrats' base matters, says Charlie Cook, an electoral analyst, because mid-term elections have much lower turnouts than elections in presidential years, so the party faithful account for a higher proportion of votes. Parties with unhappy supporters, naturally, tend to do poorly in elections, says Jeff Jones of Gallup, although more because voters switch allegiances than because they do not bother to vote at all.

Progressive activists gamely insist that they can yet recapture some of the popular fervour that carried them to thumping victories in 2006 and 2008. If only a fraction of the almost 15m first-time voters of 2008 (the vast majority of them Democrats) can be persuaded to turn out again, party organisers say, it could tip lots of races in their favour. The Democrats' healthy finances will help: the Democratic National Committee, which co-ordinates the party's campaign, is planning to spend $50m this year, up from $17m during the previous mid-terms in 2006. The Republican National Committee, its Republican counterpart, is not only poorer but in disarray.

Groups that work with young people and minorities, who tend to favour the Democrats, promise big outreach programmes. The Rev Lennox Yearwood, who runs an outfit called the Hip-Hop Caucus, argues that minorities, having tasted electoral success with Mr Obama's election, are now less sceptical about voting. Eliseo Medina of the Service Employees International Union says Latinos are so fired up about Republicans' advocacy of fiercer immigration laws, and the police harassment they fear will come with them, that they will turn out to vote for Democrats. Heather Smith of Rock the Vote, which aims to get young people to the polls, says that her organisation, having persuaded over 1m young people to register in 2008, should be able to get many of them to vote again this year.

But Mr Cook dismisses all this as wishful thinking. The elections in 2008 were unique in recent history for the number of young who voted; he cannot see that happening again. The enthusiasm gap has persisted for several months now, and is unlikely to close in the three that remain before election day, according to Mr Jones. Gallup, meanwhile, has found no discernible increase in support for the Democrats among Latinos since Arizona adopted its controversial immigration law. And the huge Democratic votes in 2006 and 2008 were always going to be hard to maintain, even in the best of circumstances.

The Democrats' best hope, in Mr Cook's view, lies not in courting the party base but in denigrating the Republicans. That may help to remind disillusioned supporters why they voted Democratic in the first place. It could also give wavering independent voters pause. But the tactic's chief benefit may lie in dampening the support of Republican cadres for their party.

Indeed, the Democrats' leaders seem to have adopted this strategy already. They are trying to frame the election as a choice between their reforms, however imperfect, and a return to the failed policies of Mr Bush. Mr Obama is likening the Republican Party to a driver who, having crashed into a ditch, waits for someone else to pull the car out and then asks for the keys back. It's a far cry from “Yes we can”.