Remember when Republicans feared the bungling diplomacy of a vain, inexperienced president and vowed to stop him before he destroyed our security? In 2014, Senate Republican leader Mitch McConnell, Ky., warned that President Barack Obama was "inflexibly clinging to campaign promises." If the novice president expected Congress to "stand idly by and do nothing while he cuts a bad deal," House Speaker John A. Boehner, Ohio, said a year later, he and his party had two words for Obama: "Hell no!"

"Our allies don't trust us; our enemies don't fear us; and the world doesn't know where America stands," went a 2015 presidential campaign ad for Sen. Marco Rubio, Fla. And one Republican foreign policy analyst even wrote that negotiations - with Iran, not North Korea - have "become humiliating, not least because our diplomatic body language is telegraphing an eagerness for a deal - any deal - with such clumsy obviousness that only the dumbest opponent could fail to notice it."

I'm fairly sure I'm quoting that last one correctly, because I wrote it, back in early 2015. And I think I was right: I remain deeply skeptical about the way the Iran deal was negotiated. But compared with the unconscionable mess that President Trump just left behind at his Singapore "summit" with Kim Jong Un, Obama's long and arduous discussions with Iran look like Klemens von Metternich convening the Congress of Vienna.

When it comes to foreign affairs - when it comes to everything, really - Trump is weighed down by inexperience, bedeviled by vanity and hobbled by impulsiveness. He's a celebrity playing at president.

He's everything, in other words, that Republicans feared Obama would be.

Going all the way back to the 2008 presidential race, Republicans were certain that Obama would be more attuned to the needs of America's worst enemies than willing to discuss the shared interests of America's best friends; this captures the destructive arc of Trump's actions from last week's Group of Seven meeting in Quebec to the spectacle in Singapore.

Republicans were scathing about Obama's immense (and obvious) self-regard. But Trump has shown himself to be beyond any of the GOP's worst nightmares about Obama. A political narcissist transfixed by his own image and utterly addicted to television coverage, Trump is unwilling to be briefed, incapable of being educated and has now blundered into a summit with a monster in exactly the way Republicans were once certain Obama would do if a camera was pointed at him.

Trump supporters will object here and argue that Obama was as bad as they think he was - and on the Iran deal, they have a point. Whatever one thinks of it now, how we got there was a lesson in bad diplomacy, with Obama quietly, desperately mortgaging American interests all over the globe to reach a grand bargain with Iran.

The difference is that Obama was pursuing a strategy. It might have been the wrong strategy, but it was a purposeful approach directed toward a major objective of his administration's policy. Indeed, his critics - with me among them - might argue that Obama was so completely focused on the execution of his overarching vision that he made avoidable mistakes and lost sight of the escalating diplomatic costs.

Trump, by contrast, has approached North Korea exactly as Republicans once feared Obama would: without a strategy, driven by TV coverage, interested only in the short-term ego boost of a photo op that does more harm than good - who gets the better end of the deal, after all, when a two-bit dictator poses side by side with the putative leader of the free world?

Obama's critics screeched about pallets of cash being delivered to Iran - I didn't like it, either - but that seems a masterstroke of diplomacy compared with Trump declaring the inhabitants of North Korea's gulags "the great winners" of the summit and halting U.S. "war games" with South Korea because, as Trump bafflingly explained Tuesday, it will save us "a tremendous amount of money" and because they're "provocative," besides. (Until now, American presidents refused to adopt the nomenclature of our enemies, referring to such operations as "joint exercises," not war games. It's exactly the kind of ignorant mistake that Republicans were certain Obama would make, starting from his first day in office.)

Trump talking to Kim, some Republicans will retort, is no worse than Obama going to a ballgame with Raúl Castro. But that comparison is merely sullen whataboutism. Unlike the Iran deal, I think Obama was right to normalize relations with Cuba, not least because the moral double-think of isolating Cuba while trading with China was a ridiculous game that even our allies refused to play after the Cold War.

More to the point, the Cuban embargo had achieved its purpose, which was to increase the costs of empire to the former Soviet Union and make the Cold War unbearably expensive. Once the Soviet hammer and sickle was lowered for the last time, America's Cuba policy had accomplished its mission.

A lot of the Republicans, however, still appalled at Obama's awkward handshake with a Cuban leader, seem to have no such unease about Trump fawning over the "talented" North Korean dictator who he says is "funny," "smart" and really "loves his country." Kim loves it so much, apparently, that it drove him, allegedly, to have his half brother killed in public with a chemical weapon and to hold American Otto Warmbier hostage, in a coma, sending him home only when he could no longer be saved. Throughout the pageantry in Singapore, Trump played it all down.

It's tiresome to have to keep noting that Obama would've been impeached for far less. But it's important to ask Republicans now: If Trump is everything you said Obama would be, what will you do about it? Some Republicans have insisted that any deal with North Korea be ratified by the Congress. Good luck with that, since Trump, like Obama, has a pen and a phone and won't hesitate to use them.

They might consider, instead, what they'd do differently if they had a chance to stop a second Obama, one who embodies everything they ever feared in foreign policy, in mid-catastrophe. They have that chance now. The only question is whether they'll take it or again succumb to blind partisanship.

Tom Nichols is a professor at the Naval War College and the Harvard Extension School, and the author of "The Death of Expertise." The views expressed here are entirely his own.