Scott Jennings, a CNN contributor, is a former special assistant to President George W. Bush and former campaign adviser to Sen. Mitch McConnell. He is a partner at RunSwitch Public Relations in Louisville, Kentucky. Follow him on Twitter @ScottJenningsKY . The opinions expressed in this commentary are solely those of the author.

(CNN) For those of us who worked for Mitt Romney in 2012, his words -- his warning, really -- about Russia will never fade.

"(Russia) is without question our No. 1 geopolitical foe. They fight for every cause for the world's worst actors. The idea that he (Obama) has more flexibility in mind for Russia is very, very troubling indeed," Romney told CNN's Wolf Blitzer on March 26 of that election year, referring to President Barack Obama being caught on a hot mic telling then-Russian President Dmitry Medvedev that after the election the United States would have more "flexibility," so long as Obama was re-elected.

Obama would use Romney's words later as a bludgeoning tool in a debate, mocking him for suggesting that Russia posed a threat to our national security.

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

His riff indicated more interest in delivering a memorized debate quip than in taking seriously the threat Vladimir Putin posed to America.

Of course, Romney was right. Based on everything we know about Russia's activities in the 2016 election, there is no doubt they meddled. There is doubt about active collusion between Russia and Donald Trump's campaign, and about whether Putin's efforts changed the election outcome.

JUST WATCHED WH: Trump has done more than Obama on Russia Replay More Videos ... MUST WATCH WH: Trump has done more than Obama on Russia 00:48

But on Putin's attempt to exploit the political and cultural divisions dividing Americans, there is no question. You have to wonder if Putin launched his operation because he knew that Obama's presidency was so divisive.

In fact, just after the 2016 election, as Obama was leaving office, just 27% of Americans who responded in a survey conducted by the Associated Press-NORC Center for Public Affairs Research saw America as more united as a result of Obama's presidency, versus 44% who said it was more divided.

Obama divided us politically. And Putin, fully aware of Obama's naiveté on Russia's geopolitical intentions, took advantage of what Obama was doing to our national unity.

After special counsel Robert Mueller rolled out his indictments of 13 Russians involved in election meddling last week, Trump -- among his other, more colorful tweets -- arrived at the right question: "Obama was President up to, and beyond, the 2016 Election. So why didn't he do something about Russian meddling?"

The reason is right in front of our face. Obama simply didn't take Russia seriously. What he said to Romney at the debate reflected exactly how he viewed the Russian threat; it will be remembered as one of the greatest presidential foreign policy failures in American history.

JUST WATCHED Schiff: Obama 'should have done more' on Russia Replay More Videos ... MUST WATCH Schiff: Obama 'should have done more' on Russia 01:16

Obama was the President when Russia decided to meddle and hack an American presidential election, and he ought to get the blame for pursuing vanity projects rather than detecting and protecting America from what was an act of war by a hostile foreign power.

National security aside, if I were Hillary Clinton or any of her supporters, I would be irate even now at Obama's failure to inform the American people fully about the Russian intrusion. Yes, I understand Obama's concerns about appearing to put a thumb on the scale. But no attack on our democracy should go unreported to the people, and besides -- everyone already knew Obama was for Clinton anyway. Election or not, the commander in chief failed to act when confronted with clear evidence of foreign interference.

Like so many other issues left to him, this is now Trump's mess to clean up. And I hope he does. He must forcefully acknowledge Russian meddling (which can easily be done without sacrificing his own legitimacy), and he must launch a presidentially appointed task force of military leaders, homeland security officials, intelligence officials, tech industry experts, election administrators and experienced campaign operatives charged with detecting and stopping Russian interference in 2018 and 2020.

I'd drag them to the Oval Office, swear them in and tell them not to come out of the Eisenhower Executive Office Building until we have a handle on stopping this foreign aggression. The optics of this would reassure the American people that a new commander in chief is not going to let Obama's failures stand when it comes to Russia.

Trump's foreign policy legacy will be measured against Obama's. That's a low bar to jump, and I hope the President and his team will do all that is necessary to protect America from future intrusions on our democracy, as his predecessor's failure is looking worse by the day.