HOLLYWOOD, Fla. (Reuters) - Reince Priebus, the unassuming head of the Republican National Committee, often plays the piano late at night, sometimes with a glass of wine nearby.

Republican National Committee Chairman Reince Priebus speaks at a general session at the Republican National Committee Spring Meeting at the Diplomat Resort in Hollywood, Florida April 22, 2016. REUTERS/Joe Skipper/File Photo

Tickling the ivories is a lifelong passion for Priebus and he has been doing it “more than usual” lately, he told Reuters in an interview last week. It’s his way of easing the stress from the most combustible Republican presidential race in generations.

It has been a rough ride for the 44-year-old party chairman from Wisconsin, who presided over a three-day meeting of Republican officials in Florida last week.

One reason for all that piano playing is the unconventional campaign being run by Republican front-runner Donald Trump. The bellicose billionaire has said that the party rules are “rigged” and could give Trump’s chief rival, Ted Cruz, a chance to become the nominee through a brokered convention, even if Trump racks up more victories in state nominating contests. He said Priebus “should be ashamed of himself.”

Yet privately, the relationship between the two has improved, their aides told Reuters. Priebus has taken frequent calls from Trump to explain nomination rules or simply hear him out, aides said.

But Priebus also has been catching fire from anti-Trump forces who want him to drop his neutrality and do more to thwart Trump’s march toward the nomination ahead of the party’s convention in Cleveland in July, when it must settle on a nominee to face Democrat Hillary Clinton or Bernie Sanders in the Nov. 8 election.

LOOKING FOR UNITY

If Trump wins the nomination - a prospect increasingly likely after his string of state victories - Priebus will need to unify his party or risk losing in November.

On Friday, when Priebus urged the party to rally around the eventual nominee, the blowback from the stop-Trump crowd was intense.

“The best way for the Republican Party to unite, win and to grow is to reject Donald Trump,” said Rory Cooper, senior adviser to a group called #NeverTrump.

Adding to Priebus’s dilemma is his task of choreographing a convention when the outcome remains uncertain. In most elections, the nomination is settled by late spring, giving party leaders time to focus on the messaging and stagecraft of the summer convention, which is typically centered on building excitement for the nominee.

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Priebus must plan for several scenarios: a traditional win in which Trump gets the 1,237 delegates he needs ahead of the convention; a contested convention in which Trump still wins; or the selection of Cruz or Ohio Governor John Kasich on a second or third ballot.

The Republican convention has not been contested since 1952 and Henry Barbour, an RNC member from Mississippi, noted it was “uncharted waters” for the party not to have presumptive nominee so late in the cycle.

Some corporations are so alarmed about how the race has turned out they have decided not to pour funding into sponsoring the convention. There also is the potential for protests of Trump in Cleveland. Trump himself has warned of riots in a contested convention.

NOT UNDER HIS SKIN

Trump’s criticism of the nominating rules has been jarring to party officials and the feud could undermine efforts to unify the party.

Colorado Republican Party Chairman Steve House said on Facebook his family received death threats after Cruz swept the state’s 34 delegates.

In private discussions with Trump, Priebus said he talks about “the daily events of the day or the week or the moment or the debate.” He also talks regularly with Cruz and Kasich.

Does Trump, with his inflammatory remarks, get under his skin?

“No, he doesn’t because I kind of know where he’s coming from. I’m not unfamiliar with his opinions. So it doesn’t really bother me because I know what the truth is,” Priebus said.

Trump senior adviser Paul Manafort said Trump and Priebus were “communicating frequently” and communicating better these days. “They don’t agree on everything but they agree to try to work things out and they are working things out,” he said.

An RNC member close to Priebus agreed.

“They’re not best buddies or anything but they have a pretty good relationship,” the member said. “I consider all this back and forth as a little bit of ‘heat of the battle’ tensions.”

Trump’s complaints about the party’s system have prompted some of his own supporters to roll their eyes in dismay.

“He ain’t read the rules,” said Ada Fisher, a retired physician and Republican National Committee member from North Carolina, who was wearing a Trump button at the Florida event.

The prevailing opinion among RNC members was that Trump is simply energizing his anti-establishment supporters, a point hammered home by Manafort, who privately told party leaders Trump is “projecting an image” and will transition to a more serious demeanor.

RNC members vow to protect Priebus from any attempt to replace him should Trump become the nominee.

“I think any effort to oust Reince will fail and it’s not the job of our nominee to select the RNC chair. It’s the job of the RNC members to select the RNC chair,” said Matt Moore, chairman of the South Carolina Republican Party.