Republicans are gathering in Cleveland, Ohio for the start of a four-day convention in which Donald Trump will try to unify a deeply divided party, and accept the formal nomination to be their presidential candidate in the November election.

No party has been so divided going into a nominating convention in at least the past 40 years. The list of no-shows at the convention illustrates the profound divide tearing at the party.

Neither of the last two Republican nominees for the White House - Mitt Romney (2012) and John McCain (2008) will be attending, nor will the last two GOP presidents - George W. Bush and his father George Bush.

Many GOP congressmen are skipping the convention as is John Kasich, the governor of Ohio - an unprecedented snub in modern US convention politics.

Kasich's snub may be the most damaging of all as Ohio is a critical swing state but especially so for Republicans - making it virtually crucial for Trump.

Slamming the Ohio governor

That Trump's campaign manager Paul Manafort chose to slam Kasich, among all of the no-shows, is telling.

He called Kasich "petulant" and said the governor was "embarrassing" his party in his home state.

Even those attending the convention seemed to be avoiding the nominee. House Speaker Paul Ryan spoke to a group of delegates from Wisconsin on Monday without mentioning Trump's name.

And there are still rebel delegates seeking a way to derail Trump's nomination. A messy floor fight for the nomination on live television would be a disaster for Trump and the party. The nominating vote is expected Tuesday with Trump's acceptance speech closing out the convention Thursday night.

For the past four decades the conventions have been little more than carefully choreographed infomericals designed to rally the party behind the nominee and galvanize voters. There was never a question about who the nominee will be.

The convention speeches are expected to attack presumptive Democrat presidential nominee Hillary Clinton for a terror attack on the US consulate in Benghazi, Libya in 2012, which left four Americans dead, including the ambassador - when Clinton was Secretary of State.

Likewise, her use of a personal email server during her time as the country's top diplomat is also going to be grist for conservatives seeking to build a case against her.

And the country's latest incidents of violence - with police killing unarmed or unthreatening black men and the subsequent revenge killings of police officers - will be put at the feet of the Obama administration and Secretary Clinton, whose campaign platform is an extension of the Obama's two-term presidency.

bik/jr (AP, Reuters)