After decisive victories by Donald Trump and Hillary Clinton in the New York primaries, Democratic leaders need to send a strong, stern message to Bernie Sanders: Back off. Stop attacking Hillary. If you want to stay in the race to propound your policy ideas, fine. But don't keep undercutting the one candidate who can save the party -- and the country -- from a President Trump.
Lately, Sanders has been going in the opposite direction. As his chances for the Democratic nomination slip away, he's turned angry and acerbic, providing Republicans with an arsenal of ammunition to use against Clinton in the fall. That's a dangerous and selfish game.
Some Republicans keep insisting they can stop Trump on their own. Clearly he fails to command a majority in his own party, with only 2 out of 5 Republicans backing him in national polls. Among all voters, his favorable rating in the latest Wall Street Journal/NBC poll stands at 24 percent, with his negatives soaring to 65 percent -- the worst showing in the history of that poll for a major presidential contender.
But suppose Trump falls short of a majority. As Robert Gates, the former defense secretary, is fond of saying: The three words not spoken often enough in Washington are, "and then what?"
Anti-Trump Republicans seem to be saying that if The Donald fails to win on the first ballot, his reaction will be: "That's fine. I concede. Have a nice day." But the exact opposite is much more likely. He'll fight like a demon and threaten to trash the party if he loses.
Add in the fact that the only plausible alternative to Trump, Ted Cruz, is widely despised in the party for his extreme policies and obnoxious personality and ran a dismal third in New York. By far, the most likely scenario is a Trump victory in Cleveland.
Which brings us back to the Democrats. Give Sanders credit: He's run a strong campaign that has energized young voters, raised vast amounts of money and exposed Clinton's weaknesses.
In the Journal/NBC poll, her negative rating hits 56 percent and only 19 percent of all voters view her as honest. Even among Democrats, only 40 percent fully trust her, down from 52 percent in October.
"The cracks are showing, and she is losing strength," says Bill McInturff, the Republican pollster who helped conduct the survey.
Some of this is Clinton's fault. By her own admission, she's handled the State Department email mess badly. And since she's been running for president since 2008, it made absolutely no sense for her to take huge speaking fees from questionable sources that could be used against her.
But Sanders is making her problem worse, precisely because he has credibility on the issue of Wall Street influence. Trump is a billionaire, with a long record of unsavory financial dealings, so his ability to attack her on money issues is very limited.
Now he doesn't have to; all he has to do is quote Sanders about her perfidy. And Bernie keeps handing Trump new material. His latest assault implies that Clinton violated campaign finance laws in her complicated dealings with the Democratic National Committee.
That comes after he questioned her qualifications to be president -- a silly but potentially damaging accusation that will certainly find its way into Republican ads next fall.
Robby Mook, Clinton's campaign manager, accused Sanders of "poisoning the well for Democratic candidates up and down the ticket," and he has a point.
"The damage is hardly fatal, but it is starting to matter, especially in Mrs. Clinton's standing with crucial independent voters," writes the Journal's Gerald Seib. Sanders' "line of attack," he adds, "seems almost designed to hit Mrs. Clinton in her area of greatest vulnerability, which is voter doubts about her honesty and trustworthiness."
Clinton offered an olive branch after New York, pointedly saying, "To all the people who supported Sen. Sanders, I believe there's much more that unites us than divides us."
Will Sanders now accept that gesture? It's virtually certain that he will never be president of this country, and that's a very hard pill for any politician to swallow after such a long and exhausting campaign. But swallow it he must.
It's time for Sanders to face reality. Who does he want running the country? Filling Supreme Court vacancies? Negotiating with foreign leaders?
Clinton or Trump?
If the answer is "Clinton," he has to start helping her, not hurting her.