David Paleologos

Special to USA TODAY

As both the Democratic and Republican national committees scramble to prepare for their summer conventions, a Suffolk University/USA TODAY poll released this afternoon shows that the Republican Party faces critical challenges, especially if Donald Trump loses the GOP nomination.

The clashing philosophies are less about tax plans, the Islamic State or building a wall, and more about the convention nominating process itself. Trump (45%) led Ted Cruz (29%) and John Kasich (17%) among GOP primary and caucus voters, with 8% undecided, according to the poll. Trump’s loyal followers are collectively thumbing their noses at the D.C. establishment and party politics, which makes the job of Republican National Committee Chairman Reince Priebus all the more onerous.

When Trump voters were asked whether a Trump convention loss would be fair and square or due to an unfairly stacked system, they said the process is unfairly stacked by a 36-point margin: 56% to 20%. A majority of Cruz voters would accept their candidate’s loss (21% unfairly stacked — 58% fair and square). Furthermore, 70% of Trump voters say that the candidate with the clear lead — even if not a majority — should be the Republican convention nominee, compared with 25% of Cruz and Kasich GOP primary/caucus voters who took that position. This poll finding sets up today’s Cruz-Kasich alliance to stop Trump at the convention.

Although these Trump voters are a small subset of the larger poll and carry a higher margin of error, they are saying that if Trump loses the nomination in Cleveland and opts for an independent run, they would follow and vote for him (56%-28%). The bad blood isn’t contained with just Trump voters. If you combine Trump, Cruz, and Kasich voters, only 60% say that they will vote for the Republican nominee if their candidate doesn’t win the nomination. The remaining 40% say they will either vote for the Democratic nominee, seriously consider an independent candidate, stay home and not vote in November, or weren’t sure. Mass defection.

In a matter of weeks, Priebus has to figure out how to prevent an embarrassing general election visual like a convention walkout or worse, a riot.

About the only thing Trump, Cruz and Kasich voters agree on, according to the poll, is that the eventual GOP nominee should be someone who ran for the nomination this time around. A clear majority of all three groups of voters agree on that. Apparently, so does House Speaker Paul Ryan.

Democratic primary and caucus voters are also split, with Hillary Clinton leading Bernie Sanders 50% to 45% nationally thanks to stronger majorities among minority and older voters. Fifty-two percent of Clinton voters said that Sanders should withdraw if she were to clinch the nomination, while 39% said he should not. Most Sanders voters (71%) said their candidate should continue to the Democratic National Convention no matter what, while 21% said he should not.

In a reverse image of the division on the Republican side, Clinton voters, by a tally of 51% to 24%, said that if she loses the nomination it would be fair and square whereas Sanders voters said that if he loses, it would be because the system was unfairly stacked against him (28% “fair and square” versus 53% “unfairly stacked against him”). The loyalty factor on the Democratic side is somewhat better than the 60% figure on the Republican side. When you combine Clinton and Sanders voters, 69% say that if their candidate were to lose the nomination they would still vote for the Democrat, while the remaining 31% will either vote Republican, independent, stay home in November, or weren’t sure.

Poll: Trump, Clinton face divides in their parties even if they win nominations

Despite their personal preference, 8% of Clinton voters believe that Donald Trump can defeat Clinton in the general election, but a considerable 33% of Sanders voters believe Trump could beat Clinton. This poll perception is already etched in the minds of a third of Sanders voters. And it’s an issue that Democratic National Chairwoman Debbie Wasserman Schultz has to be mindful of when coordinating the logistics in Philadelphia.

And speaking of the general election, there is the possibility of outright defections to the opposing party based on what voters say they would do right now if they had to choose. The poll tells us that 7% of Trump voters would support Hillary Clinton over Ted Cruz if he were the nominee. And 16% of Trump voters would select Bernie Sanders over Cruz.

Don’t laugh — 13% of Sanders voters say they will vote for Donald Trump against Hillary Clinton. If Trump were to lose the nomination, 19% of Sanders voters would choose Cruz over Clinton; and if John Kasich were the nominee, 23% of Sanders voters would vote for the Ohio governor over the former secretary of State.

David Paleologos is director of the Suffolk University Political Research Center in Boston.