WASHINGTON -- Republicans spent four days last month in Cleveland, listening to speeches, cheering their nominee, and watching the balloons drop.

Could they wind up doing it all over again?

Assembling their convention delegates for the second time this year is one of the two ways the Republican National Committee could pick a new presidential nominee if Donald Trump gives up the ghost and he leaves the race.

There have been calls from some Republican quarters for the party to abandon Trump, most recently by Joe Scarborough, co-host of "Morning Joe" on MSNBC and a former Republican congressman from Florida, after the GOP nominee suggested that "Second Amendment people" might want to take action to stop Democratic nominee Hillary Clinton from nominating judges who would uphold gun control measures.

In addition, a series of polls following both conventions give Clinton an edge over Trump both nationally and in key states, including by double digits in Pennsylvania.

Trump, of course, has shown no signs of quitting. But one thing everyone's learned in this upside down presidential year is that anything's possible.

"This would require them to just start over," said Craig Engle, founder of the political law practice at the lawyer-lobbying firm Arent Fox LLP and former National Republican Senatorial Committee general counsel. "Maybe not so much with all the fanfare, but it is going to require the Republican National Committee to convene and nominate a candidate."

Republican National Committee spokeswoman Lindsay Walters said only: "The party is responsible for filling any vacancies. At this time there are no vacancies."

GOP Rule 9 gives the national committee the power to "fill any and all vacancies which may occur by reason of death, declination, or otherwise of the Republican candidate for president of the United States or the Republican candidate for vice president of the United States, as nominated by the national convention."

The RNC can do that by either reconvening the national convention or by limiting the gathering to the state party chairs and national committee members. In the latter case, the three officials from each state combined would cast the same number of votes that the state's convention delegation did in Cleveland.

For New Jersey, that's 51 votes to be cast by party chairman Samuel Raia, national committeeman Bill Palatucci and national committeewoman Virginia Haines.

If the three party officials can't agree on a nominee, the votes would be split, with each one casting one-third of the state's votes. Under that scenario, Raia, Palatucci and Haines each would get 17 votes.

If they needed a replacement, Republican officials would have no shortage of candidates to choose from, including Indiana Gov. Mike Pence, the vice-presidential nominee; those Trump vanquished during the GOP primary -- such as Texas Sen. Ted Cruz, Ohio Gov. John Kasich and Gov. Chris Christie; or top Republicans who didn't run this year, like House Speaker Paul Ryan of Wisconsin and 2012 GOP nominee Mitt Romney.

Should party officials ask the convention delegates to decide, most of them no longer would be pledged to a candidate since this would technically be the second ballot. That means no candidate could lay claim in advance to a substantial number of votes and a brokered convention could actually happen.

After a candidate is selected would come the rush to put the new candidate's name on the ballot in all 50 states and the District of Columbia. Each state has different deadlines for putting names on the ballot.

But judges traditionally have allowed parties to make a substitution even after ballot deadlines have passed, lest voters be prevented from choosing their preferred candidate.

Just look at New Jersey in 2002, when Democratic U.S. Sen. Robert Torricelli, beset by ethics problems, withdrew at the last minute. The state Supreme Court allowed the party to substitute former U.S. Sen. Frank Lautenberg, who went on to victory.

Courts even could order states to reprint ballots, or rule that a vote for the former candidate will be considered a vote for the new one, said Brett Kappel, who handles political law at the lawyer-lobbying firm Akerman LLP.

"The courts in these types of situations are sensitive to the fact that allowing the individual to vote for the candidate of their choice is the most important issue here," Kappel said. "The courts are going to prevent anybody winning by default."

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant. Find NJ.com Politics on Facebook