NOT all the major polling models give Republicans a clear edge to capture the Senate this autumn, but most do. The New York Times’ “The Upshot” puts the chances at 65%, Nate Silver of FiveThirtyEight most recently called it “in the neighborhood of 60-40” and the Washington Post’s “Election Lab” gives the GOP a 51% shot. Sam Wang of the Princeton Election Consortium is the outlier, giving the Democrats a 70% chance of holding the majority. The obvious reasons for the GOP’s advantage are technical, as we wrote earlier this month. More vulnerable Democrats are up for re-election this year than vulnerable Republicans. The GOP needs to take away six seats from the Democrats, and is already nearly assured of winning three; of the six or seven competitive races (depending on who’s counting), Republicans must win just three to gain a majority. Add in Barack Obama’s low approval ratings and the fact that the out-of-power party generally does better in midterm elections, and you have a nice bloodless political-science description of the Republican advantage.

Yet the technical factors don't quite explain why Democrats feel so listless this autumn. Democratic spin doctors trying to get upbeat media coverage are resorting to state-by-state descriptions of specifics that play in their favour. It is true that things look better for Democrats at a granular level, which is why Mr Wang thinks they will hold the Senate. And the Democrats’ technology-driven ground game, which added a percentage point or so to Barack Obama’s vote total in 2012, may do so again this year. But when Democratic flacks promote these sorts of inside-baseball stories, it only highlights their lack of a persuasive overarching political narrative. This autumn, it is simply not clear what the Democrats want, or what they are promising to do for the people they want to vote for them.

It is not that people do not know, in general, what Republicans and Democrats stand for. Americans know that Republicans believe in lower taxes, less regulation of business, fewer government benefits and tighter immigration rules, and that they want to repeal Obamacare and oppose action on climate change. They know Democrats believe in more generous public benefits, action on climate change and the environment, looser immigration rules, and preserving or expanding Obamacare and raising taxes on the rich. Voters identify Democrats with minority and women’s concerns, and Republicans with the concerns of whites and men. But Democrats aren’t running strong campaigns that tie in coherently to any of those themes. There is no clear national vision of what Democrats would actually do if they manage to hold the Senate.

In Iowa, for example, Bruce Braley, a Democratic congressman, is locked in a dead heat with the Republican candidate, Joni Ernst, a state senator. Mr Braley is generally described as the most left-wing of the new Democratic Senate candidates this year. Yet his chief campaign issue is only modestly liberal: preserving the government’s system of subsidised student aid for college. Mr Braley notes that Ms Ernst supports privatising the federal government’s low-interest Direct Loan programme, and calls this a “reckless, Tea Party plan”. Ms Ernst’s campaign responds that privatisation could be “backstopped” by the federal government, sparing students any increase in interest rates. Mr Braley’s selection of this issue seems reasonably smart, and was clearly guided by the fact that Ms Ernst herself received federal aid to get through college. It allows him to tie her to the increasingly unpopular Tea Party movement, and plays to the established perception that Democrats are more likely to defend public benefits for the poor and middle class. But this is a small-bore issue, and the pitch is defensive: Mr Braley is warning that the Republican candidate will eliminate existing programmes, rather than promising any new ones.

It isn’t surprising that Democrats aren’t promising much, since they lack the capacity to deliver anything. Whether or not the Democrats retain the Senate, the past two years have demonstrated that legislation on any major issue will die in the Republican-controlled House. Pragmatic Republicans have been entirely stymied by their party’s Tea Party wing, which will not countenance any compromise with Democrats. Democrats’ hopes for progress on key issues such as immigration and climate change have come to rest on executive action by the president, but that prospect is so politically risky that Mr Obama may decide to delay any major initiatives until after the elections.

The pivotal condition here is the impossibility of getting Tea-party Republicans to vote for any new legislation that has been approved by Democrats, and the inability of more pragmatic Republicans to bypass the extremists. In the 2012 elections, the Obama administration had a theory of change: what was needed was to “break the Republican fever” over taxes. The Republicans’ rigid opposition to raising any form of taxes, ever, was what made any form of new government programme impossible, went the theory; using the expiration of the Bush tax cuts to force them to abandon that pledge would open the possibility of negotiation and compromise on other issues. This theory turned out to be wrong. The tea-party Republicans’ resistance to compromise has rendered the House incapable of passing even legislation to address an urgent humanitarian border crisis, with tens of thousands of children trapped in immigration limbo.

In the face of the far right’s effective veto over the congressional GOP, Democrats have given up on passing any significant legislation either until they regain control of the House, an impossibly remote prospect, or until the Tea Party somehow withers away, which shows no signs of happening. The Democrats’ acceptance of their inability to accomplish anything significant has left them unable to campaign on big themes. The party feels exhausted, still convinced of the need for immigration reform, climate change legislation and expanded benefits for the middle class, but unable to imagine a political pathway to get there. If the Democrats lose the Senate this fall, it may be technically due to an unlucky roster of elections and the traditional midterm setback for the party in power. But it will also be a verdict on the party’s inability to conjure a sense of élan or vision in the face of the political paralysis tea-party Republicans have induced.