The Republican convention is Donald Trump's last chance to prove himself

It is more than likely that the tactics employed by the already polarising Mr Trump will serve only to deepen America’s social partitions

Donald Trump has chosen Mike Pence as his vice-presidential candidate (AP)

Set against events that suggest a world tearing itself apart – Brexit, the Bastille Day slaughter in Nice, a failed coup in Turkey, not to mention the racially charged revenge shootings of police in the US itself – an American political convention, with its pre-packaged glitz and basic function as a four day party infomercial, seems a sideshow.

But the Republicans’ gathering in Cleveland this week is anything but a sideshow. In a narrow sense, it represents Donald Trump’s best chance to create a semblance of unity within the party he has hijacked. Far more important, it may be the last opportunity for the businessman/showman to prove he is remotely fit to lead the most powerful country on earth.

Nothing he has done so far suggests that he is. Even the unveiling of his vice-presidential choice, Governor Mike Pence of Indiana, was a mess. Such occasions are second only to conventions themselves as stage setters for the final battle for the White House. Instead Mr Trump, as usual, spent most of the Pence roll-out talking about himself. The unintended message could not have been clearer: Mr Pence, who in six months could find himself the proverbial heartbeat from the presidency, was little more than the afterthought of a narcissist.

History does not repeat itself, Mark Twain said, but it rhymes – and it is easy to draw parallels between Cleveland 2016 and Chicago 1968, site of the Democratic convention whose chaos symbolised the most traumatic year in recent American history. Ultimately Richard Nixon prevailed, with his appeal to the “silent majority” of his countrymen who craved a return only a return to normality.

There will be protests this week in Cleveland, but its streets will not resemble those of Chicago half a century ago when Mayor Richard Daley’s police effectively declared war on demonstrators. And while two shootings of police officers within 10 days have set the US on edge, the mood is not comparable to 1968, riven by turmoil over Vietnam and shocked by the assassinations of Martin Luther King and Robert Kennedy.

Similarities exist nonetheless. “Make America Safe Again” is a theme of the convention, and Mr Trump, Nixon-like, presents himself as the law and order candidate. President Obama, he says, “doesn’t have a clue” over how to respond to the crisis. The US, he maintains, is nothing more than “a divided crime scene” spinning out of control, desperate for the strong leadership that only he can provide.

It is more probable that such tactics from the already polarising Mr Trump will serve only to deepen America’s divisions. By the same token, the world beyond will be anything but re-assured. For the Republican Party, which has always advertised itself as tough on crime and tough on America’s enemies, security at home merges naturally with security abroad. But the Trump approach, an inchoate mix of nativism, militaristic bluster and protectionism, will merely rattle America’s allies while providing openings for rivals like Russia and China.

There is no sign Mr Trump has ever thought more seriously about foreign policy than he has about domestic issues like gun control and abortion. He speaks from the hip, ad-libbing and frequently contradicting himself within the space of a single week, even a single day.

A convention above all is a platform for the candidate, a showcase not only for himself but his policies. It requires planning and discipline, not to mention the teleprompters that Mr Trump so disparages. This week he has a last chance to redeem himself. But will he take it?

The omens are not good.