As Napoleon is reputed to have said, never interrupt your enemy when he is making a mistake. So why are Republicans seeking to impeach Joe Biden when he’s looking increasingly capable of losing next year’s presidential election all by himself?

We will never know what kind of president Biden would have made in his prime, but it is clear that his prime was passed some time ago. It has become painful to watch the President interact with people or make a speech – even with prompt cards at the ready. This week, his press secretary Karine Jean-Pierre was moved to call a premature end to a press conference he had attempted to hold in Vietnam on his way back from the G20 summit, after he began rambling. His own team tried to drown him out by playing music as he continued to speak. ‘I’m going to bed,’ he eventually declared and left the podium.

If only it could have been a metaphor for a retirement that looks long overdue. On Monday, the 22nd anniversary of 9/11, he intimated that he had been at Ground Zero in New York the day after the atrocity – when history records he was in Washington all day.

Biden’s frail performances have not been lost on the public. A CNN poll last week found that three-quarters of the American people are ‘seriously concerned’ about his mental and physical fitness for office.

When the campaigning begins in earnest next year, there is little chance that Biden will suddenly discover reserves of cogency. Yet for some Republicans it is not enough to let the President make the case against his own re-election. They are trying instead to change the narrative from one of incapability to one of malfeasance. The House Speaker Kevin McCarthy this week announced he is to launch a formal impeachment inquiry into Biden’s involvement in the dubious business dealings of his son Hunter.

A House oversight committee, directed by Republicans, has spent months trying to connect Biden père to the sins of Biden fils. A fairly substantial amount of evidence has been produced – shockingly under-reported outside of America’s conservative media – to show suspicious financial connections between foreign entities and the Biden family. There are also highly credible testimonies that the then vice president Biden joined multiple telephone calls between Hunter and his associates and clients – and there is the mystery of the various email aliases that Biden Sr used at the time.

None of this, however, represents a smoking gun. The key question is whether, as many right-wingers believe, Joe did in fact co-operate with his son’s schemes to cash in on his father’s considerable power – or whether Hunter was merely selling the illusion of influence. If it is the former, Republicans would be quite right to say that Donald Trump was impeached for much less. Indeed, it’s an intriguing irony that Trump’s first impeachment stemmed from his attempt to find out exactly what Joe did in connection to Hunter’s business activities in Ukraine.

But what do Republicans hope to achieve by dragging America through another impeachment? At best, they will help to undermine one of Biden’s chief selling points in 2020: the idea that, in contrast to Trump, he is a fundamentally decent man. Yet if they fail to turn up any damning evidence they will end up looking desperate. Worse, they will drag US politics further into the mire of partisanship into which it has already sunk.

Impeachment is a process that was built into the US constitution to allow the urgent removal of a clearly malign president who refuses to stand aside – and, as such, is expected to command broad bipartisan support. Now, it is becoming almost routine – a political wheeze by which impatient opponents seek to remove a president from office rather than wait for the electorate to carry out the task. A blatantly political impeachment stands zero chance of success, because members of the House and Senate will vote along party lines – and the removal of a president from office requires a two-thirds majority in the Senate.

Impeachment has become, then, a purely symbolic act. Moreover, the US public has already shown itself to be unimpressed by the employment of ‘lawfare’ in political matters. Trump was never widely popular, yet every move by his Democratic opponents to try to get him in the dock – something they have now achieved – has only served to galvanise support among his base and draw sympathy from independents who abhor the misuse of the justice system.

An obsessive campaign to impeach Biden over his son’s business dealings will doubtless do the same for the President. Unless his involvement in Hunter’s business dealing can be shown to have reached a threshold of criminality, his supporters may well start asking: was it really so wrong to want to help his son to succeed when Biden has suffered so much familial tragedy – his first wife and daughter dying in a car crash when he was a newly elected senator, and his other son, Beau, dying of brain cancer in his forties?

The Democrats are currently stuck down an electoral cul-de-sac. The Commander-in-Chief is unfit for the job, but cannot see it and seems determined to run for re-election. But where are the credible challengers? Biden’s vice president, Kamala Harris, is even less popular than him. Gavin Newsom has an appalling record as governor of California. With Trump cruising towards the Republican nomination for next year’s election, it’s clear that a crisis of political leadership afflicts left and right.

But Biden’s political future should be decided by the American people. If Republican schemers try to seize that right from the electorate it makes it more likely that he will dodder on – to the detriment of his party, his country and the wider world.