Republicans finally have an issue on which they can legitimately criticize President Biden. In a new Pew Research Center poll, only 27 percent of Americans say that Biden’s handling of Afghanistan has been good or excellent. Even some Democrats are quite critical of the president. This is a golden opportunity for the GOP to try to reclaim its credibility as a serious party on national security.

And yet it is blowing this chance by falling prey to the same compulsions — carelessness with the truth, cynical opportunism, mindless posturing, excessive outrage, rank prejudice, blatant hypocrisy — that have been its hallmarks in the Trump years.

The fundamental problem for the GOP is that it knows what it’s against — whatever Biden has done — but it has no idea what it’s for. Appearing on Fox Business on Tuesday, former president Donald Trump fulminated about “the level of incompetence on this withdrawal.” But when pressed on how he would have handled Afghanistan, the best he could come up with was: “We should have hit that country years ago, hit it really hard, and then let it rot.” Huh? Trump went on to say “We should have withdrawn in a totally different way” without specifying what that way was.

The problem for Trump and the Trumpkins is that the Biden pullout from Afghanistan is merely a continuation of the Trump pullout. It wasn’t Biden, after all, who set a deadline for withdrawal, had his secretary of state meet with the Taliban or forced the release of 5,000 terrorists. That was Trump.

This leads Republicans into mind-boggling hypocrisy. On April 13, Sen. Josh Hawley (R-Mo.) tweeted: “President Biden should withdraw troops in Afghanistan by May 1, as the Trump administration planned, but better late than never. It’s time for this forever war to end.” And yet on Aug. 26, Hawley demanded Biden’s resignation after 13 service members were killed at the Kabul airport while carrying out the evacuation of U.S. citizens and Afghan allies. “Joe Biden is responsible,” he insisted.

In essence, Hawley is calling for Biden to resign for implementing Trump’s policy — as if the hopelessly incompetent Trump could have done it any better. And Hawley is far from alone. Even before the suicide bombing, a plethora of Republicans who praised Trump for leaving Afghanistan were demanding that Biden be removed from office for leaving Afghanistan. These are the same people who insisted that two impeachments of Trump for committing “high crimes and misdemeanors” — which are not in evidence in Afghanistan — were an assault on democracy and a grievous distraction from more urgent priorities.

Rather than confront the obvious inconsistencies in their arguments, most Republicans simply omit any mention of Trump in their anti-Biden screeds. There are only a handful of exceptions — honest Republicans such as Rep. Liz Cheney (Wyo.) who admit that this is a “Trump/Biden calamity,” not a partisan Democratic policy.

Republicans can’t make up their minds: Do they wish that Biden had exited faster and better or never exited at all? As my Post colleagues Paul Kane and Mike DeBonis note, a few hawkish House Republicans have called for the the United States to maintain a presence at Bagram air base, but many of their MAGA colleagues disagree.

Republicans also can’t decide if they want to castigate Biden for leaving Afghan allies behind — or for bringing them here. It is hard for the GOP to make the case that it cares about the fate of Afghanistan when the loudest voice in the room — Fox “News” host Tucker Carlson — is employing the white supremacist “replacement theory” to warn against allowing Afghans into the United States. On Tuesday, Carlson said that “thanks to meticulous and thoughtful planning, Operation Change America Forever came off precisely according to plan.” (Left unexplained is how, at most, 120,000 refugees could change a nation of 333 million.)

In lieu of serious policy positions, the GOP prefers silly and specious claims. Many on the right promoted an Internet video posted by a self-described comedian purporting to show a man being hanged from a helicopter by the Taliban. “This horrifying image encapsulates Joe Biden’s Afghanistan catastrophe,” Sen. Ted Cruz (R-Tex.) tweeted. No, it doesn’t. It was apparently a Taliban attempt to fix a flag. (Cruz has since deleted the tweet.)

The GOP is also vastly exaggerating the amount of U.S. military equipment left behind in Afghanistan. The total figure isn’t $85 billion, as Trump claimed, but less than a third of that amount — and much of the equipment is inoperable or obsolete.

Why make so many contradictory, deceptive and downright dishonest criticisms of Biden? The reality is grim enough, but, after years of demagoguery and falsehoods, Trump and his followers simply can’t help themselves. In the process they are making clear that the GOP still cannot be taken seriously on national security matters.