“After months dominated by the Republican circus of haters, ranters and that very special group of king killers in Congress,” the Democrats — the adults in the room — finally got to debate, harrumphed the New York Times editorial board in October 2015.

And sure, the GOP debates were, as the old saying goes, not their circus and not their monkeys, as far as the self-satisfied left was concerned. But now the liberal circus has come to town, and — unlike Republicans, who had leaders like Paul Ryan and Ben Sasse and Mike Lee and Mitt Romney to at least try to provide adult supervision — the absence of grownups is impossible to ignore.

Since Donald Trump’s victory over Hillary Clinton, Democrats’ behavior has been sad to watch.

On the mild side of the insanity is the focus on Clinton’s popular-vote lead. In a New York Times piece about how to talk to your family over Thanksgiving, one of the talking points was that Hillary won the popular vote. But why? Winning the popular vote is the equivalent of losing the World Series but scoring more total runs than the winning team.

Even President Obama went down this road during a speech in Peru a few weeks ago: “More votes have been cast for Democratic congressional candidates than Republican,” he claimed — a ridiculously ignorant and nonsensical metric that grade-school students, let alone a president, should know to disregard.

It’s fairly easy to laugh at this childishness, even from the famously petty president of the United States. But the left’s road trip to Crazytown took a darker turn when accusations that Russia hacked the election results to make Trump president were made by formerly “respectable” voices and given oxygen by the media and Democrats.

Third-party liberal candidate Jill Stein last week launched a fundraiser ostensibly to get enough cash to file for a recount in three close states: Michigan, Wisconsin and Pennsylvania. Yet as the money rolled in from gullible leftists, she kept raising her cash target. Heading into the weekend, it stood at $7 million, a threefold increase from its not-so-humble beginnings.

Stein is, quite clearly, running a “scam-PAC” — a political action committee designed to bilk supporters of their hard-earned cash and laugh all the way to the bank, while building an email contact list for future fundraising endeavors. Stein even confirmed she couldn’t “guarantee” the money would be spent on a recount. Even if a recount were forced, the extra cash would stay with Team Stein.

Worse, the DNC is allowing it. Donna Brazile tweeted, “As Interim chair of the DNC, I have received info and more regarding #AuditTheElection. At this time, the DNC has not issued any statement.” For one of our two major parties to “no comment” accusations of a stolen election should concern all Americans.

During one of the general-election debates, Trump was asked whether he would accept the results if he lost. He famously said, “I will tell you at the time. I’ll keep you in suspense.”

He was rightly pilloried from all corners. The RNC was quick to put out a statement that they would “accept the results and the will of the people.” Trump’s daughter Ivanka, his running mate, Mike Pence, and even his own spokesperson put out statements that the results would be respected. Trump supporters like Hugh Hewitt criticized him, saying, “It is outside the norm of American political rhetoric to express a contingent acceptance of the result.”

Hillary herself responded, “That’s horrifying.” So where’s that horror now that her supporters carry “Not My President” signs and Stein runs a scam-PAC aimed at Hillary’s own voters?

Where are the Democratic Party’s grownups? Their silence suggests they think it benefits them to keep their supporters angry. That’s no way for people in leadership roles to behave. America needs two strong political parties that take our values and institutions seriously and not just when they win — after all, that’s what the Democrats said when they thought Republicans were being intransigent.

“Give Trump a chance” has been the post-election mantra from his supporters, but Democrats don’t have to even give Trump a chance: They simply need to accept reality. And the reality is that a free and fair election, using long-established rules, gave the presidency to Donald J. Trump. They can oppose his policies and fight his ideas, but they should stop trying to destroy our political system in the process.