AS AN illustration of what ails congressional Democrats, Nancy Pelosi’s recent attempt to defend an 88-year-old party grandee who was alleged to have shown up to work in his pyjamas, fondled generations of female employees and to have asked at least one of them to “touch it”, is hard to beat. The Democrats’ long-serving House leader, who is merely 77, had been asked on NBC about the allegations against Representative John Conyers of Michigan, the House’s longest-serving member. She responded by calling him an “icon”. Asked whether she believed his accusers, Mrs Pelosi blustered: “I don’t know who they are. Do you? They have not really come forward.” At least five former staffers of Mr Conyers, who was until this week the ranking Democrat on the House judiciary committee and a force in the Congressional Black Caucus, had at that time accused him of inappropriate behaviour. One had received a pay-off from his office funds.

That Mrs Pelosi should be tarred by the culture of impunity sex pests have been enjoying on Capitol Hill is, in a sense, cruelly unfortunate. As a successful Speaker of the House between 2007 and 2011, and the first woman to fill that role, she has done a lot for women’s empowerment. She was also quick to realise her error. Her office put out a corrective statement shortly afterwards and Mrs Pelosi has since said she believes at least one of Mr Conyers’s accusers, while in private she has urged the octogenarian congressman to resign, as he probably soon will. Yet her instinctive refusal to condemn him also reflected another sort of impunity, for too long enjoyed by the House Democrats’ aged and complacent leaders, even as their party has become increasingly diminished and resentful of their command.

Even if the Democrats did not urgently need to attract younger voters to compensate for the meltdown in their working-class base, the fact that the average age of their House leadership is over 70 would seem problematic. Consider why this is, and it looks far worse. Mrs Pelosi and her fellow leaders are sustained by a sclerotic patronage system, of which her pandering to Mr Conyers was indicative, which has banished accountability and fresh talent from the upper reaches of the party. For her part, Mrs Pelosi remains in many ways an impressive leader—she is a relentless fundraiser and adept caucus manager, at once pragmatic and acceptable to the Democrats’ ascendant left. Yet given that her party is as unpopular as Donald Trump, and that she is the prime beneficiary of one of its main structural weaknesses, she is probably doing the Democrats less good than harm.

The offending system is itself testament to the cost of ducking difficult decisions. For while power has become increasingly centralised in both parties in recent decades, the Democrats have muddled that transition by maintaining some of the architecture of a more fragmented past. Where House Republicans have abandoned seniority rules and imposed term-limits on the chairing of congressional committees and subcommittees, for example, the Democrats have refrained. Those plums have duly been captured by a minority of increasingly aged Democrats in safe seats, an arrangement the well-organised black caucus has fiercely guarded. Most other Democratic House members, meanwhile, face increasingly arduous fights for survival, in a toxic political environment, with little prospect of leadership any time soon. Had Barack Obama won and hung onto the Illinois House district he once sought to represent, he might still be waiting to advance beyond the House energy committee, where his vanquisher in that primary contest, Bobby Rush, plies his trade.

No wonder many talented Democrats, recently including Rahm Emanuel, Kirsten Gillibrand and Chris Van Hollen, have quit the House at the first good opportunity. “At the end of each cycle, you ask yourself, ‘Is what I can achieve worth the personal, financial and emotional cost?’” asks a former Democratic member of Congress, who concluded it was not. House Republicans have serious problems of their own, but at least a churn of congressional talent; the Democrats are by contrast a stagnant pool. The result is that one of the best reasons for retaining Mrs Pelosi is that there is no one obvious to replace her. This is insane.

Dissatisfaction with Mrs Pelosi within her caucus runs deep. On the basis of the unprecedentedly stiff leadership challenge she faced after the general election from Tim Ryan, a burly Ohioan, at least a third of House Democrats want her out. Yet few of the dissidents dare say publicly why she should go. Most blame the Republicans—as Mr Ryan did—by arguing that she has become so demonised by the right as to be repellent to swing voters. Yet while that is true, and a source of Republican glee, there is no proof it hurts the Democrats electorally. Only three people matter in House races, the candidates and the president. Given the Republicans’ appetite for personal destruction, moreover, Mrs Pelosi’s successor would in no time be similarly traduced. So here are four better reasons for Mrs Pelosi to move on.

Quit while you’re ahead

First, no Democratic leader has been held accountable for nearly a decade of withering defeats for the party, including the reduction of its House representation to the lowest level since the 1920s. If Mrs Pelosi was serious in arguing, after her Conyers blunder, that politicians should be held to the same standard of accountability as the rest of us, she should belatedly take the hit. Second, her patronage nexus and controlling leadership style are obstacles to the reform and infusion of talent and ideas her party needs. Third, on a related note, much of that effort should be directed to reconnecting with working-class voters, at which Mrs Pelosi, who appears to think the minimum wage a boon for them, rather than a policy to help the lowest paid, is ill-suited. Fourth, her contribution to the Democratic Party has been immense. It would be a shame to sully it by overstaying her usefulness more than she already has.