Rubio’s relationship to his signature accomplishment is more complex than Walker’s. It is, in fact, more like Romney’s. Although he still stresses the need for immigration reform, Rubio has disavowed the structure at the heart of the Gang of Eight bill — the immediate legalization of millions of illegal immigrants while security measures are being put into place. Now, Rubio advocates putting security into place — and ensuring that it is up and running — before legalization.

That’s a huge change; no Democrats would have supported the Gang of Eight had it been structured in that way. But the Gang of Eight bill was far more than just a sequence of measures. It was a sprawling, 1,000-page-plus reworking of the nation’s immigration system. Rubio’s bill would have dictated the organization of even the tiniest details of immigration in the United States…

There is more in the Gang of Eight bill that GOP opposition researchers will likely mine if Rubio’s candidacy catches fire. It’s a long bill; there will be a lot to criticize.

None of the troubling details in the bill may sink Rubio’s chances of winning the Republican nomination, but it’s a pretty fair bet he won’t embrace them during his campaign. And if Rubio does become the Republican standard bearer, the party could again find itself in the uncomfortable position of running a nominee who disavows his own signature accomplishment.