In the event that voters grant the Republicans control of one or both houses of Congress, it looks like we can expect a good bit of snarling from President Biden. His frustration with his party’s prospects certainly boiled over on Saturday when he described a group of peaceful protesters as “idiots.”  

During a speech at Joliet, Illinois — at an elementary school, of all places — Mr. Biden remarked that he’d read the messages outside the event, where one placard said, “Socialism sucks.” Said he: “I love those signs when I came in. ‘Socialism.’ Give me a break. What idiots.”

The president seemed to be forgetting that the Democratic Party has high-profile members, such as Senator Sanders and Congresswoman Alexandria Ocasio-Cortez, who identify as socialists. His flash of temper reminds of the outbreak  when he called someone “fat,” “a damn liar,” and “too old to vote,” and labeled another “a lying, dog-faced pony soldier.”

 A new round of insults might be a feint in an election where the president has chosen not to run on his record. Instead he’s positioning the midterms as a referendum on democracy. It would have been wiser to take the high ground, which runs through that mythical land of unity that he promised when campaigning.

Over the past two years, Mr. Biden has doubled down on the “mean tweets” strategy he decried in his predecessor. In his September speech at Philadelphia’s Independence Hall alone, he insulted the “MAGA Republicans” and the opposition party as a whole. 

The president used a version of the word “threat” nine times and of “extreme” six, charging his opponents “do not respect the Constitution,” “believe in the rule of law,” or “recognize the will of the people.” It’s this last phrase that Mr. Biden could be forced to swallow after Tuesday’s results are tabulated.

When in the midterms of 2006 the Republicans suffered what President George W. Bush called a “thumping,” Mr. Bush reacted with civility. “I understand when campaigns end and I know when governing begins,” he told a reporter who asked how he’d work with the Speaker-Designate, Nancy Pelosi, who had called him “incompetent, a liar, the emperor with no clothes, and … dangerous.”

He pledged to “work with people of both parties,” saying “if you hold grudges in this line of work, you’re never going to get anything done.” Seated next to Mrs. Pelosi days later, he said, “We will not agree on every issue but we do agree that we love America and that we are concerned about the future, and that we will do our very best to address big problems.”

In 1994, when Republicans won control of the House and the Senate, President Clinton followed a similar script, describing how he’d “called the leaders of the next Congress, Senator Dole and Congressman Gingrich, to tell them, after this hard-fought campaign, that we are ready to work together to serve all the American people in a non-partisan manner.” 

The New York Times reported that, in private, Mr. Clinton, “was frustrated, raging, and depressed.” In public, though, he backed “the Republican goal of balancing the budget” after my former boss, Dick Morris, and pollster Doug Schoen advised him “to embrace fiscal conservatism to become relevant” to voters such as those who’d supported the Reform Party’s presidential candidate, H. Ross Perot, and suburban independents. 

“If Mr. Biden doesn’t do a mid-course correction,” Mr. Schoen told me, “after what I expect will be a ‘shellacking,’ in the words of President Obama on Tuesday, then it will be calamitous for his presidency as well as the Democratic Party.” 

Anger at losing big will be best expressed in private or be left to journalists, like ABC anchor Peter Jennings, who said “voters had a temper tantrum” in 1994. As CNN’s Don Lemon advised President Trump on responding to an angry citizen, “[T]ake it, just as President Bush and others did.” 

Mr. Lemon added: “Take it. It’s part of what you signed up for when you decided to descend that escalator and throw your hat in the ring for president.” 

How will Mr. Biden take a rebuke? He’ll have only two choices. Continue to insult and nurse a grudge or follow the admonition he delivered to Republicans two days ago: “You can’t love your country only when you win.”