Jeb Bush and his allies seem determined to take Rubio down with them:

The super PAC supporting Jeb Bush released a new advertisement attacking Marco Rubio on Monday, accusing the Florida senator of changing his position on immigration reform and supporting “amnesty.”

It’s fair to point out that Rubio is unreliable and can’t be trusted on immigration. This is not only a true accounting of his record, but it is also a perfectly fair criticism of someone who has made a point of trying to use other candidates’ records on immigration against them. Regardless of what one thinks immigration policy should be, Rubio has shown that he will trim his sails to side with whichever side of the debate seems to be most advantageous to him at the time, and he will just as easily abandon that side when it ceases to be useful. No matter what side one takes in the immigration debate, Rubio is a lousy ally to have.

That said, Bush and his allies are the least credible attackers on this issue, since Bush has always been even more pro-immigration than Rubio. Bush’s complaint against Rubio is that Rubio was just smart enough to run away from an unpopular immigration bill, and he thinks it is a selling point that he has never wavered in supporting legislation on immigration most Republicans reject. Bush is trying to hurt Rubio by correctly saying that the latter is an opportunist, but in the process his allies just remind everyone that he is even more at odds with Republican voters on this issue than Rubio is. Bush and his allies may help to sink Rubio with this attack, but that is all they will accomplish. By attacking Rubio as “pro-amnesty,” his Super PAC is arguing that Republican voters should reject Bush at the same time.