By Cokie Roberts and Steven V. Roberts

President Trump says many things that are wildly exaggerated or flat-out false, but he told one of his biggest whoppers at a recent White House news conference. “Just so you understand,” he boasted to reporters, “the Republican Party is very, very unified.”

In truth, the Republican Party is very, very fragmented, pulled apart by competing factions defined largely by their relations to Trump, whose outsized ego and undersized competence eclipse the political sun and darken all debate.

This festering fratricide could jeopardize the GOP’s congressional majorities in elections next year. Even if Republicans maintain control, their ability to run the government could be even more weakened than it already it is. And that’s saying a lot, since party leaders have produced exactly one notable achievement this year: Neil Gorsuch’s elevation to the Supreme Court.

On one side are the True Trumpians, led by Steve Bannon, the president’s former consigliere, who recently told Sean Hannity on Fox News that that he is “declaring war on the Republican establishment.” He has vowed to oust Senate Majority Leader Mitch McConnell and support primary challengers against any GOP senator who does not swear allegiance to Trump’s brand of economic nationalism — as defined by Bannon, of course.

“Nobody’s safe; we’re coming after all of them, and we’re going to win,” he crowed.

The other side of this civil war is more splintered and less bellicose, but just as motivated. Recruits range from Never Trumpians like Ohio Gov. John Kasich, who refused to vote for the nominee of his own party, to former Trumpians like Tennessee Sen. Bob Corker, who have grown increasingly alarmed by the president’s impulsive and reckless behavior.

In a stunning interview with The New York Times, Corker said Trump’s “volatility” risks putting the country “on a path to World War III.” Asked whether other Republicans shared his fears, Corker said, “Oh, yeah. Are you kidding me? Oh, yeah. … The vast majority of our caucus understands what we’re dealing with here.”

Since Corker is not running again, he’s freed from political considerations, but the “vast majority” of Republican lawmakers fear a primary challenge from Bannon’s jihadists. That means they won’t join the public denunciation of Trump, no matter what they feel in private. And they all share with Trump a common need: writing a record of accomplishment they can take to the voters. But the voices of dissent within the GOP are still startling.

Sen. Jeff Flake of Arizona, a prime Bannon target, wrote a book excoriating fellow Republicans for not standing up to Trump. “Rather than defending the enduring principles that were consonant with everything that we knew and had believed in, we pretended the emperor wasn’t naked,” Flake writes. “Even worse: We checked our critical faculties at the door and pretended that the emperor was making sense.”

Sen. John McCain was clearly referring to the president when he denounced as “unpatriotic” those who follow “some half-baked, spurious nationalism cooked up by people who would rather find scapegoats than solve problems.”

Sen. Ben Sasse of Nebraska accused Trump of violating his oath to uphold the Constitution by threatening to punish media outlets that cover him critically. “No president should play with censoring news they dislike,” he tweeted.

These are the voices of reason that Bannon wants to purge from the party, an approach that deeply alarms Republican leaders like McConnell. In at least four states, he notes, Republicans lost Senate seats in recent years because they nominated hardline conservatives that “were not able to appeal to a broader electorate in the general election.”

The lesson is clear, says McConnell: “You have to nominate people who can actually win, because winners make policy and losers go home.”

Yet Trump waffles, praising Bannon as a “friend of mine for a long time” while hinting he may try to “talk him out of” his suicidal crusade. The president does not seem to grasp the essential truth that McConnell is preaching: that elections matter.

If Republicans lose control of Congress, Trump’s agenda — and judicial nominations — are doomed. And if Democrats capture congressional committees, endless investigations and possible impeachment proceedings will dominate the rest of Trump’s tenure.

If Bannon’s insurgents actually win, the consequences could be equally damaging for Trump. More bomb-throwers in Republican ranks is the last thing he needs.

Trump fueled the civil war in the Republican Party, and as a campaign tactic, it worked well. But governing requires compromise, not chaos; negotiation, not napalm. And the firestorm he deliberately ignited could wind up consuming him.

Steve and Cokie Roberts can be contacted by email at stevecokie@gmail.com.