David M. Drucker is a senior political correspondent for the Washington Examiner and a CNN political analyst. The views expressed in this commentary are solely those of the author.

(CNN) Just like that, Barack Obama weakened Mitt Romney and solidified his lead in a presidential contest that just a few weeks earlier had threatened to spin out of his control.

In a line of attack that has assumed a mythology all its own, Obama early in his third prime time debate with Romney cut down the Republican nominee for something he had written in his 2010 book, "No Apology: The Case for American Greatness."

"When you were asked, what's the biggest geopolitical threat facing America, you said 'Russia.' Not Al-Qaeda; you said Russia," Obama charged . "And, the 1980s are now calling to ask for their foreign policy back, because, the Cold War's been over for 20 years."

Every debate has a defining moment ; for instance, Ronald Reagan's "there you go again" in his 1980 debate with Jimmy Carter. In 2012's debate on foreign policy, Obama's barb, and Romney's failure to recover, was it. Romney's momentum evaporated in an instant.

Normally, that would be the end of the story. But then Americans elected Donald Trump.

The New York Republican's unusual embrace of Russian strongman Vladimir Putin, during the campaign and since he entered the White House, has kept Washington's fraught relationship with Moscow on the front burner.

Trump seems intent in following in the footsteps of his predecessor, Obama, and his Democratic opponent for the presidency, Hillary Clinton. He's instigated his own "Russian reset" despite grave warnings from Republicans in Congress, famously crystalized by Romney, to get tough with Putin.

Ironically, Trump briefly considered nominating Romney for secretary of state. The hire might have signaled a reversal, leading to a Russia policy grounded in the understanding that Moscow continues to aggressively undermine US interests and a first meeting between Trump and Putin at the G-20 in Hamburg, Germany, that addressed that fact.

Instead, Trump continues to cozy up to Putin and ignore Russia's belligerence, escalated during Obama's second term, dismissing the legitimacy of multiple investigations into Kremlin meddling in the 2016 campaign to boost the Republican over Clinton.

The President claims, counter to US intelligence community reports , that it's unclear who did the meddling -- if there was any meddling at all. After all, as Putin told him, if Russia did it, it never would have been detected by American intelligence.

"Somebody said later to me, which was interesting. Said, let me tell you, if they were involved, you wouldn't have found out about it. Okay, which is a very interesting point," Trump told reporters on July 12, just after news broke that his son, Donald Trump Jr. held a previously undisclosed meeting in June 2016 with Russian individuals that was attended by his campaign chairman Paul Manafort and Jared Kushner, his son-in-law and top White House advisor.

And so there's a new appreciation for Romney among a previously skeptical political press corps. Some Democrats have even apologized for mocking and ignoring Romney's assertion that Moscow is the biggest geopolitical threat to US interests.

"Bravo @MaxBoot for calling out Putin lovers in Trump's GOP. We Dems erred in '12 by mocking Boot/Romney Russia worry." Brian Fallon, a Democratic operative (and CNN contributor) who served on Hillary Clinton's 2016 campaign and is a veteran of the Obama Justice Department, offered that concession via Twitter

Said Jon Favreau, a former Obama speechwriter a few days later on an episode of "Pod Save America," a podcast he hosts with other Obama alumni: "I'm willing to say that in 2012, when we all scoffed at Mitt for saying that ... Russia was our No. 1 geopolitical foe -- I think we were a little off there."

What Romney camp feared

The Romney campaign anticipated plenty of attacks on the former Massachusetts governor heading into the fall general election debates.

Callous businessman, made millions buying and selling companies, sometimes approving massive layoffs to make them profitable? Check. Flip-flopped on key positions? Check. Twitter uproar over some gaffe or another -- real or deemed so by the media? Check.

Romney's carefully calibrated -- and consistently held -- position that Russia was an international menace? It didn't even warrant special attention during the governor's intense debate prep session, say Republican operatives who worked on his campaign.

The one-term ex-governor and former venture capitalist didn't have a lot of hands-on foreign policy experience, which Obama clearly aimed to exploit. "I know you haven't been in a position to actually execute foreign policy..." the President said at one point.

But Romney had given the matter serious thought -- and never wavered.

As was his habit, he had studied the issue. So meticulously crafted was the language he used to frame his foreign policy views about Russia that it wasn't happenstance that he referred to Moscow as the greatest geopolitical "foe" and not greatest geopolitical something else.

Lanhee Chen, Romney's top policy advisor from the 2012 campaign, explained it to me in a telephone interview from Palo Alto, California, where he works as a Hoover Institution fellow and Stanford University professor.

"Gov. Romney was very careful with his words," he said. "He chose the term 'geopolitical foe' deliberately, because he wanted to differentiate the challenge posed by Russia from other significant national security threats, like radical Islamic terror or North Korea's nuclear weapons program. The phrase 'geopolitical foe' was meant to evoke a game of Chess, where an opponent is trying to counteract or block every move you make. That's what he was trying to convey by characterizing our relationship with Russia in that way."

"By the time we got to debate prep, he already felt very strongly about this," Chen added.

Blindsided

The Romney campaign was blindsided by the reaction.

They entered the spin room that evening on the campus of Lynn University, in Boca Raton, Florida , figuring that Obama's dismissive attitude toward Putin underscored his weakness on national security and provided them an opening.

It didn't work out that way, as they soon discovered.

The press corps covering the campaign, print, television and otherwise, saw Obama as the winner of the exchange -- the clip played as a sort of endless Romney bloopers loop for days afterward -- and, well, voters tended to agree.

While Romney's team disagreed, they also felt that the issue ultimately wasn't central to the outcome of the race.

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Five years later, the Romney alumni can occasionally be caught enjoying a sense of satisfaction watching Democrats evolve into staunch Russia hawks, which they take as vindication for the candidate and the campaign that they poured so much of their heart and soul into.

After Russia blocked in the United Nations Security Council a US proposal to stiffen sanctions on North Korea, I tweeted , "Imagine that, Russia is not our friend. Who knew?" To which Stuart Stevens, Romney's top political strategist on the 2012 campaign replied : "I know a guy who pointed this out in 2012."

Correction: The debate at which Barack Obama challenged Mitt Romney on Russia was the third presidential debate in 2012; an earlier version of this article incorrectly attributed it to an earlier debate.