Remember when Republicans wanted to stand up to Vladimir Putin?

Remember when the Republican Party was a reliable foe of Russia's autocratic leaders? It actually wasn't that long ago. When President Barack Obama forged the New Start treaty with Moscow in 2010, Republican leaders opposed the treaty in part because Russia under Vladimir Putin could not be trusted with an arms control agreement.

Now the Republican nominee for president in 2016 is suggesting he may not honor U.S. commitments to NATO, which exists to counter Russian aggression. In an interview with the New York Times, he said he would come to the aid of Baltic states if they were attacked by Russia only if “they have fulfilled their obligations to us.”

This is not a unique position. The view that America should not necessarily honor its mutual defense agreements in NATO is popular among many foreign policy academics, particularly those in the “realist” school. Many progressives too, like the editors of the Nation magazine, have mused that America's push to expand NATO is the root cause of Putin's aggression in Ukraine. Pat Buchanan, the former White House speechwriter (and the force who resurrected the pre-World War II mantra of “America First”), also thinks NATO's expansion has baited the Russian bear.

Just what is the U.S. obliged to do in defense of NATO partners? Most Americans probably would not support a shooting war to defend the independence of Estonia, Latvia or Lithuania. But the treaty does not spell out in detail what other NATO members would be required to do in the face of an attack. Until recently at least, most Republicans understood that the best way to prevent that nightmare scenario was through deterrence. That requires publicly embracing its mutual defense obligations without spelling out precisely what that would mean.

Or it used to require that. As former House Speaker Newt Gingrich told CBS on Thursday: “I'm not sure I would risk a nuclear war over some place which is the suburbs of St. Petersburg. I think we have to think about what does this stuff mean.”

Comments like that from Trump are not so surprising. But Gingrich actually understands what he is saying. Gingrich is one of the reasons NATO expanded in the 1990s to include Eastern Europe and eventually in 2004 to add seven states, those “suburbs of St. Petersburg.” He pushed for legislation to do just that when he was speaker of the House.

Here's Gingrich in 1996: “Since its creation in 1949, NATO has been expanded on three separate occasions. In the spirit of a safer, freer and more secure world, the time has come to once again enlarge NATO's membership. For 45 years, NATO has met its mission under the leadership of both Republicans and Democrats, evolving as circumstances on the international front have changed. This is one of those moments in history when change is necessary to meet a greater need.”

When Russian irregulars invaded Ukraine in 2014, Gingrich urged President Barack Obama to do much more. An op-ed he co-wrote with Sen. Lindsey Graham, R-South Carolina, asked: “When will the administration put its might where its mouth is: When Kiev is in flames? Or never?”

Keep in mind, this is what Gingrich said when Russia attacked a non-NATO member. Now he's not sure the U.S. should defend the three Baltic nations who are in the alliance and in good standing.

Despite the outcry of many Republicans like Gingrich in 2014 that Obama was doing too little to defend Ukraine, the president in the end did deploy forces and military assets to many of the front-line states in the NATO alliance. This creates a kind of trip wire if Russia ever were to attack these countries with conventional forces. It is an example of deterrence, a concept of statecraft that Republicans used to understand.

It's worth asking whether Donald Trump or Gingrich would say now that Obama went too far - that he took too much of Gingrich's advice. After all, as the former Bloomberg View columnist Josh Rogin reported last week, Trump apparats stripped language from the Republican platform that called for lethal defense assistance to Ukraine.

There are two ironies in all of this. The first is that this squishiness on Russia is coming from a nominee who poses as a super hawk. The same guy who muses about killing the families of terrorists is open to abrogating America's treaty commitments to an alliance that has prevented a major European war for the last 70 years. We have to suspect his hawkish proposals are just for show. (Michael Hayden, who served as CIA director under George W. Bush, and John Brennan, who is currently CIA director, have both said they would not implement such an order.)

But the second irony is that Trump's stated position on NATO puts him far to the left of Hillary Clinton, who as secretary of state implemented a “reset” in relations with Russia that was opposed by most Republicans. The argument at the time was that Obama was allowing Putin to get away with his 2008 invasion of Georgia and inviting more aggression down the road.

Clinton has since changed her tune, after those warning proved prophetic in 2014 with Russia's invasion of Ukraine. She compared Putin at the time to Hitler.

Today it's the Republican nominee who would let Putin get away with an invasion of Ukraine. He's not even sure whether he would stand up to the Kremlin if Putin invaded a member of NATO.

Eli Lake is a columnist for Bloomberg View.