At the very start of Donald Trump's farcical presidential campaign, he did the rival Democratic Party a great favor by tarnishing the entire Republican brand with his irresponsible smear of Mexican border-crossers.
Now he has done his own party a favor by knifing his own unwelcome candidacy with his outlandish attack on Sen. John McCain, denigrating the Vietnam War hero's service as a combat pilot in the 1960s and more than five years as a prisoner of war.
In an interview with Republican pollster Frank Luntz at the Family Leadership Summit in Iowa, Mr. Trump knocked the idea that McCain was a war hero. Then he allowed that he was a war hero "because he was captured," adding snidely, "I like people that weren't captured." He made no mention of Mr. McCain's injuries in the crash that led to his capture, nor to the torture he endured as a POW in Hanoi.
The remarks were particularly grating coming from a man who received student and medical deferments from military service in Vietnam. Mr. Trump had already been feuding with Mr. McCain, apparently offended because the senator had said Mr. Trump had "fired up the crazies" with his incendiary remarks on Mexicans.
Mr. Trump then poured more fuel on the fire by criticizing Mr. McCain's work in the Senate for veterans, compared to what Mr. Trump contended he did himself in their behalf.
At first, it fell to Lindsey Graham of South Carolina, Mr. McCain's best friend in the Senate, to blow the whistle on Mr. Trump for his assault on Mr. McCain. Other GOP presidential aspirants held back, perhaps not to offend party conservatives competing with Mr. Trump for the anti-immigration vote.
But The Donald's recklessly insensitive assault on Mr. McCain, the party's 2008 standard-bearer, finally stiffened the others' spines. Former Texas Gov. Rick Perry, himself a veteran, declared Mr. Trump unfit to be commander-in-chief and called on him to immediately withdraw from the 2016 presidential race.
Mr. Trump, however, has vowed to press on, also declining to rule out running as a third-party candidate if not nominated as a Republican. His verbal antics and presence as a personal wrecking ball may continue to be a disruption, but the other candidates need no longer to treat this self-constructed pariah with kid gloves.
Nevertheless, Sen. Ted Cruz of Texas, who has been a defender of Mr. Trump on anti-immigration policy and obviously is seeking support from the same conservative constituency, has refused to criticize him. He told reporters that he recognized that members of the press "love to see Republican-on-Republican violence" and wanted to hear him "say something bad" about Messrs. Trump or McCain, but "I'm not going to do it" because each man "is a friend of mine."
Republican National Committee Chairman Reince Priebus, who earlier had phoned Mr. Trump urging him to tone down his rhetoric in the interest of the party, left it to an RNC spokesman to say Mr. McCain is an American hero, and "there is no place in our party or our country for comments that disparage those who have served honorably." So much for muzzling Trump the Terrible.
Finally some other GOP presidential candidates are popping their heads out of the sand. According to the Washington Post, Jeb Bush has tweeted "enough of the slanderous attacks." Scott Walker has called on Mr. Trump to apologize to Mr. McCain, and Marco Rubio has written that POWs "deserve much better than to have their service questioned by the rantings of Donald Trump."
As for Mr. Trump himself, he seems set on following a modern-day version of a scorched-earth policy. Impervious to the flames licking at his own heels while blackening the reputation of the party, he can't seriously think the Oval Office is in the cards for him with such antics. But who knows what he thinks, or cares?
The latest Washington Post-ABC News poll actually has Mr. Trump leading the pack, with 24 percent of likely Republican voters surveyed, to 13 percent for Mr. Walker and 12 for Mr. Bush. Mr. Graham, an also-ran in the poll, had direct advice for Mr. Trump Tuesday on the CBS News morning show: "Run for president, but stop being the world's biggest jackass!"
With the first Republican television debate looming barely two weeks off in Cleveland, Mr. Trump clearly holds a ticket of admission going to the top ten in the polls. It's an invitation to more GOP mayhem that he won't pass up.
Jules Witcover is a syndicated columnist and former long-time writer for The Baltimore Sun. His latest book is "The American Vice Presidency: From Irrelevance to Power" (Smithsonian Books). His email is email@example.com.