It seems to me that Rubio has made a major mistake with his immigration attacks on Cruz. While he may or may not be successful in convincing folks that he and Cruz at one time shared the same stance on immigration, he has made certain that everyone knows that he was and is for amnesty for illegal immigrants currently in the country and that he teamed up with Schumer, Obama, and the other pro-amnesty folks; many of whom, by the way, are not pro-amnesty because they want to help people out, but are pro-amnesty because they think offering amnesty will help change the American culture by marginalizing–and perhaps eventually eliminating–liberty and other values on which this country was founded.
Of course, my guess is that Rubio thinks that the winning strategy is not to convince folks that Cruz is pro-immigration, but to convince them that Cruz is someone who can’t be trusted and therefore Rubio is the better choice, even if he is more moderate and pro-amnesty. But making that case successfully is somewhat dependent on delving into the arcane tactics of legislative debate and thus is a tall hill to climb and, ultimately, since it isn’t true makes it perhaps an insurmountable challenge.
Rubio should’ve stuck with painting himself as a conservative instead of, in attacking Cruz, highlighting his moderate and establishment credentials.