As Republicans gather in Cleveland for the convention this week to officially name Mr Donald Trump as their candidate for the presidential election, one big question remains: Will the party be able to unite behind him?

Party insiders have been struggling in the weeks since the New York real estate tycoon wrapped up the nomination to fully back their chosen nominee. And that is threatening to put a big damper on an event normally used as a rousing kick-off for the party's general election campaign.

For a start, the convention in Cleveland will be missing some of the major names who normally grace these occasions. The Republican Party's only two living former presidents, Mr George H.W. Bush and Mr George W. Bush, will both be sitting it out, as will former Florida governor Jeb Bush.

The party's two most recent nominees, Mr John McCain and Mr Mitt Romney, will also be notably absent. Even Ohio Governor John Kasich, a losing candidate in the recent primaries whose state is hosting the party soiree, has decided he does not want to be involved in the floor proceedings to officially nominate the businessman.

Instead, the initial list of speakers for the convention is packed with Trump family members and loyalists. All four of Mr Trump's adult children and his wife, Melania, are scheduled to speak.

And though the reality TV star promised to bring some showbiz glitz to the convention, the line-up of celebrities due to show up was greeted with limp enthusiasm this past week.

No instantly recognisable names - such as Clint Eastwood, who turned up in 2012 - are on the list. The sole actor on it is Antonio Sabato Jr and the most prominent businessman is controversial PayPal co-founder Peter Thiel.

All of that adds up to increasing doubts about Mr Trump's drawing power and the formidable challenge he faces to change the narrative.

"There are many visible splits. Many prominent and top establishment Republicans are staying away from Cleveland largely because they don't like Trump. He will need a smooth convention to have any chance of bringing them back into the fold," American University School of Public Affairs adjunct professor Richard Benedetto told The Sunday Times.

"So far, party leaders have been tepid rather than enthusiastic in their support for Trump. Again, if the convention goes well, that 'tepidity' could change for the better. If not, it will remain."

In addition, convention organisers have been beset by fund-raising shortfalls, with expected contributions from large corporations such as Coca-Cola, PepsiCo and Apple failing to come in. The Republican National Committee even had to deal with embarrassing reports that it had made an urgent last- minute request for US$6 million (S$8 million) from Las Vegas billionaire Sheldon Adelson.

While the speaker and donor lists may be the most outwardly visible signs of trouble, Republicans have other concerns as well.

The party's rules committee has spent much of the week leading up to the convention fighting a rebellion from the #NeverTrump movement. The fervently anti-Trump faction of the party launched an 11th-hour attempt to sabotage his nomination by pushing for a rule change that would allow delegates to vote for whichever candidate they wanted to.

A marathon 15-hour meeting last Thursday night finally killed the effort, meaning Mr Trump is set to officially secure the nomination when delegates at the convention vote tomorrow.

"We crushed them. NeverTrump is nevermore," Mr Trump's triumphant campaign chairman Paul Manafort told CNN last Friday.

But the fact that factions of the party are still pushing for an alternative at this stage speaks poorly of the candidate's performance so far.

Finally, some party leaders are concerned that a large turnout by protesters might cause chaos at the convention. Tension is already high as the event takes place just weeks after racially divisive shooting incidents in the United States and days after a deadly terror attack in France.

But while the potential for disappointment at this year's convention is very real, observers have said it still presents an opportunity for the Republicans to make gains if the event goes off successfully.

Dr Larry Sabato of the University of Virginia said: "If (the) unconventional approach works with the public, it is possible Trump will take at least a temporary lead in the polls. The burden will then be on (Hillary) Clinton to put on a good show (at the Democratic convention) in Philadelphia that can catapult her to a renewed lead..."