Sen. Rand Paul (R-Ky.) has shifted on a number of important issues in recent years. (Photo by Chip Somodevilla/Getty Images)

Sen. Rand Paul's best window for winning the 2016 Republican presidential nomination increasingly looks like it has passed.

A lot can happen over the next 18 months, but the renewed focus on foreign policy -- and more specifically, the Islamic State -- has reminded the Republican Party where its true views on international affairs lie.

And it is decidedly not with non-interventionists like Paul (R-Ky.).

A new poll from CNN/Opinion Research is the best we've seen to date bearing out this point. The poll asks Americans to identify themselves as either hawks or doves -- hawks being someone "who believes that military force should be used frequently to promote U.S. policy" and doves being those who think "the U.S. should rarely or never use military force."

Overall, it's close, with 50 percent picking the doves and 45 percent picking the hawks.

Among Republicans, though, it is decidedly not close. About seven in 10 (69 percent) say they are hawks, while just one-quarter (25 percent) side with the doves. That's nearly three-to-one.

The poll mirrors a Pew survey from earlier this month which showed the number of Republicans pushing for a more active role in international affairs -- a good approximation for hawks -- rising from 18 percent to 46 percent in a matter of nine months. Others have shown the same trend.

Now, you can argue until you're blue about whether Paul should be considered a dove. And you can point out that Paul has actually carved out a relatively hawkish position on combating the Islamic State.

And indeed, the Paul camp says the hawk/dove dichotomy is a false choice. "Foreign policy isn't that simple," spokesman Doug Stafford told The Fix. "Sen. Paul is neither hawk nor dove but rather a conservative realist who will defend America and our interests when necessary, but also not have us police the world or intervene in every conflict around the world -- positions most Americans agree with."

That's fair. Paul is nothing if not a few shades of grey, and he doesn't really subscribe to his father's brand of non-interventionism. But if you had to insert Paul into one of the two groups enumerated by CNN, it would clearly be the doves. There's no way he would fit in with the hawks.

And this will be the contrast that will be driven home by every hawkish GOP presidential candidate anxious to be the most anti-Rand Paul candidate in the 2016 field -- and they are legion. In order to overcome the perception that he is more closely aligned with the doves, Paul would really have to pull some foreign policy jiu jitsu.

As it stands, with increasing scrutiny of Paul's political consistency, the Islamic State rearing its ugly head in the Middle East, and the GOP base reverting to a war footing, it's increasingly hard to see how Rand Paul fits into his party's future plans for 2016.

And the campaign begins before you think.