The writer, a professor of government at King’s College, London, is author of ‘Britain and Europe in a Troubled World’

Donald Trump has become the first American president to be impeached twice. He now faces a Senate trial on charges of inciting insurrection.

But impeachment is a clumsy weapon. It confuses the juridical with the political. It is also ill-suited to the problem posed by a divisive and dangerous president who is anyway on his way out of the door. Tying up the first days of Joe Biden’s presidency with this process would be a mistake.

Like so much in the US constitution, impeachment’s roots lie in medieval England. Parliament used it in the 17th century when there seemed no other way to bring someone holding office under the Crown to book.

Britain last used impeachment in 1806, although Adam Price, a Plaid Cymru MP, sought to revive it in 2004. His plan to impeach then prime minister Tony Blair, over allegations of misleading parliament on the Iraq war, was supported by a small number of backbenchers — including current prime minister Boris Johnson. But the resolution was never debated in the Commons.

Impeachment is rarely used in parliamentary systems for an obvious reason. It derives from a period before the development of modern political parties, when MPs were regarded as a collection of disparate individuals brought together to adjudicate on the public good, including matters of justice.

Today in the UK and other parliamentary systems, juridical issues are kept separate from partisan politics. The UK prime minister is accountable politically to voters and to the House of Commons, which can force him out with a vote of no confidence. Juridically, he is accountable like all citizens to the law of the land, and can be prosecuted for misconduct in public office. In September 2019, Lord Macdonald, a former director of public prosecutions, declared that Mr Johnson could face prison were he to defy parliamentary legislation, which did not in the end pass, requiring him to delay Brexit. That stand-off was avoided.

In presidential systems, where the head of government is elected separately from the legislature, impeachment is more frequent, particularly in Latin America. In Brazil, President Dilma Rousseff was impeached in 2016 on grounds of budgetary mismanagement. She claimed that it was a political coup, a substitute for the vote of no confidence that is not possible in separation of power systems. Heated recriminations persisted for years.

If history is any guide, the current attempt to hold Mr Trump accountable for the violent mob that stormed the US Capitol last week would become mired in the same claims.

The US constitution allows impeachment for “misdemeanours” as well as “high crimes”, but does not say what that means. A partisan Congress is hardly in a position to supply a neutral definition. In 1970, Gerald Ford, then the Republican leader in the House, suggested it was “whatever a majority of the House of Representatives considers it to be at a given moment in history”.

In the absence of agreed rules of evidence and clear standards of proof, there is real danger Mr Trump’s fate would be decided on a partisan basis. In the three prior presidential trials — Andrew Johnson in 1868, Bill Clinton in 1999 and Mr Trump last year — the Senate did not vote to convict. In 2020, one Republican senator, Mitt Romney voted to convict, and Republican Senate majority leader Mitch McConnell openly admitted, “I’m not an impartial juror. This is a political process”.

By contrast, in 1974, when it became clear that sufficient Republican senators were likely to vote to convict Richard Nixon, he pre-empted the process by resigning. This week, 10 Republicans broke ranks and voted for impeachment and Mr McConnell has left open the possibility of voting for conviction.

But that does not necessarily mean a Senate trial is the right course of action. The constitution is silent on whether a sitting president can be indicted in the courts for a criminal offence. The general consensus is that he cannot as that would violate the constitutional separation of powers: the courts are the third branch of government.

There is no doubt a former president can be indicted for crimes committed while in office. Ford, who replaced Nixon as president in 1974, pardoned his predecessor to avoid such criminal prosecution. Ford was excoriated for this decision, but it was the right one as it enabled a much needed process of healing to begin.

America desperately needs a similar process of healing today. Mr Biden has pledged to bring the nation together. Allowing him and Congress to concentrate on reviving the flagging economy and addressing the pandemic would help make that promise real.

Were Mr Trump to be convicted by the Senate, many of the 70m Americans who voted for him would be convinced the outcome was a political vendetta. It would make him appear a martyr. The alleged wrongdoing should instead be dealt with by the courts, not politicians. Perhaps, however, it would be better to pardon him, allowing him to sink into disgraceful oblivion.