More proof that the post-Iraq War hangover, which had become a defining feature of the Democratic Party, is beginning to lift was evident on Sunday when one key Democratic Senator, Rhode Island’s Jack Reed, conceded that the reintroduction of U.S. ground forces into Iraq may eventually become necessary if the threat ISIS poses to the American interests grows.

In his appearance on CNN, Reed was very careful not to advocate for the use of U.S. troops in Iraq. In fact, he said on two occasions that the most effective use of American military power was a careful supplementation of Iraqi and Kurdish ground forces with U.S. air power.

Reed was clear that a “specific” threat to American interests, not a general threat of terror, would be necessary before officials considered escalating American involvement in Iraq. If that threat was real and urgent, he added, “then I think we have the obligation to go in and take out that threat.”

The American political press has taken notice:

The problem with this assertion is that a justified use of U.S. ground forces to neutralize a threat to American interests has already been met, according to the Obama administration. The attempt to use Special Forces and air power to covertly free American hostages in ISIS custody met the threshold justifying the use of American forces which Reed described. That mission failed and the threat to American interests materialized in a video featuring the beheading of journalist James Foley, but that was a threat that Washington determined could not be resolved by foreign proxies.

What sort of threat would meet Reed’s requirements? One suspects that this would be a moving target. Maybe a verified and imminent threat to Western interests in the form of a terrorist attack? That sort of rock solid intelligence is tough to come by, and more often a terrorist attack only appears imminent in hindsight. What about geostrategic considerations, like the prospect that the Iraqi army may fold and Baghdad might fall? While that would be among the gravest developments in Iraq in years, Reed did not appear warm to the prospect of U.S. ground troops bailing out Iraqi authorities.

Reed seemed theoretically amenable to the prospect of a new mission in Iraq which may be characterized by ground forces, but the devil is always in the details.