The outcome of the GOP presidential primaries could turn in part on the question: Who hates amnesty more, Ted Cruz or Marco Rubio?

The two candidates are locked in mortal combat over this question, in the wake of their big dust-up over immigration at Tuesday night’s debate. There are many layers to this argument. To get caught up to speed, read Benjy Sarlin, Sahil Kapur, and Byron York. This may seem like a debate over legal arcana, but as Sarlin notes, this is “a critical conflict in the race, both on policy and politics.”

The central question is this: Was Marco Rubio right when he charged during the debate that Ted Cruz has no business attacking him as soft on “amnesty,” because Cruz, too, supported legalization back in 2013?

To date, those making this claim have not actually produced proof of it. Yet it’s important for Rubio to make that charge stick, because if he can, it could muddy the waters and make it harder for Cruz to draw a sharp contrast with Rubio’s previous support for the Barack Obama-Chuck Schumer comprehensive reform bill, i.e., SCHUM-OBAMNESTY.

That bill contained a path to citizenship, which Rubio has backed away from and struggled to atone for ever since. Cruz argues that only he is the true foe of amnesty, because unlike Rubio, he never supported legalization for the 11 million. Rubio is saying, Oh yes you did, Senator!

The argument that Cruz backed legalization at one point rests on a series of public statements that Cruz made in 2013, when he was trying to get his amendments included on the Schum-Obamnesty bill. Those amendments would have beefed up border security and would have stripped the path to citizenship out of the bill, while leaving legalization in it, thus precluding citizenship completely for all undocumented immigrants who would become legalized. As Sahil Kapur details, plenty of evidence from the time suggests that Cruz was employing a “poison pill” strategy to kill the bill because there was no way Democrats would ever support his additions.

Cruz and his supporters have stuck to this explanation, with some of them pointing out that Cruz was merely trying to expose the fact that Dems just wanted citizenship to win millions of new voters. The idea was that, if Dems really wanted to bring all those people out of the shadows, they’d accept just legalization, per one of Cruz’s amendments. The fact that they wouldn’t proved their real agenda: gaining new voters.

There are a series of public statements that Cruz made at the time that do seem — at first glance — to complicate matters. But none of them proves Rubio’s point. Let’s run through them:

1) In 2013, Byron York asked Cruz if his amendment “would allow” legalization. Cruz responded that allowing legalization would be “the effect” of his amendment. But all that means is that Cruz’s amendment would not reverse the bill’s legalization component; it would merely “allow” it to remain. That fits comfortably with Cruz’s suggestion that he was trying to call the Democrats’ bluff on citizenship. After all, the amendment could not have called the Dem bluff without leaving legalization in the big bill.

York then asked Cruz if he does “buy in to this whole legalization idea.” Cruz responded that “legalization is the predicate of the Gang of Eight bill,” but added that his effort would “improve that bill so that it actually fixes the problem.” This could easily mean nothing more than that his amendments would beef up the bill’s border security. After all, the whole anti-amnesty line is that the real problem that actually needs fixing is that the border is out of control.

2) Much has been made of video of Cruz in 2013 in which he discussed his precluding-citizenship amendment. In it, Cruz argued that those who are concerned about “the 11 million who are currently in the shadows” should support his amendment, because “the effect” of it would be to allow them to be legalized, which the proponents of reform claim to want. Cruz claimed that reform probably would not ultimately pass Congress without citizenship being precluded.

But again, this fits comfortably with the idea that Cruz was calling the Democrats’ bluff: If they wanted legalization, they should have been willing to accept an amended bill that precluded citizenship but left the bill’s legalization component in place. Cruz also said: “I want immigration reform to pass.” But all this means is that Cruz wanted it to pass so he could get his components of an amended bill (the nixing of citizenship; beefed up security) passed, not because he wanted legalization. This is just more bluff-calling.

3) National Review produced a 2013 exchange in which Cruz was asked if he’d grant legal status. He responded: “The amendment I introduced…did not affect the underlying legalization in the Gang of Eight bill.” By this Cruz easily could have meant that his amendment did not resolve the legalization question either way. And it didn’t! Yes, Cruz could have stated his opposition to legalization outright at this point, and didn’t. But that doesn’t mean he endorsed it.

Some have argued that Cruz deliberately left his position on legalization ambiguous, to be more electable in a general election later. I’ll grant that this might be true, but even if it were, it does not mean Cruz actually supported legalization, which is the crux of Rubio’s claim. Also, as Ramesh Ponnuru notes, even if Cruz did leave that ambiguous, he has now removed all ambiguity, flatly coming out against legalization.

The central intra-GOP dispute this whole flap highlights is the same old question: Should the 11 million stay, or should they go? If they are to be allowed to stay, on what conditions? Rubio backed a special path to citizenship at one point and currently leaves the citizenship option open, to be attainable at some unspecified point later. Cruz — based on what has come to light so far — never explicitly backed legalization, pushed to preclude citizenship, and now has come out against legalization, too.

The bottom line remains that Cruz can legitimately claim to have been a far more ardent — and consistent — foe of amnesty than Rubio ever was, from 2013 on down to the present.