I like Santorum on a few issues, but problem is he is un-electable in 2016. He is not inspiring many voters. Check his poll numbers.
Trump started off great with his candid and unprecedented remarks about the American victims of criminal alien crimes and that Mexico is where most of them are coming from. This was all contained in a 2011 GAO report, but it was news to the MSM despite the millions of Americans who have been victims.
Trump refused to apologize, rightfully, but the heat got to him and now he is flopping around on the issue like a fish out of water. He felt compelled to say he loved Mexicans, wants more legal immigrants, and came up with the Mike Pence touchback scheme to give most of the illegals amnesty. Most of the other Rep candidates like Cruz who favor amnesty, now say that they will discuss the fate of the lawbreakers already here after the border is secured. It is now deemed the safe response. Trump may revert to that once he gets skewered during the first debate.
Trump is actually acting like a politician. He wants to be loved and will say anything to get people to like him. He just hasn't learned yet how to parse his language so that all sides think he is agreeing with them. If Trump had said attrition thru enforcement, he would have locked up the nomination. Now he will be talking in circles trying to figure out how to get out of the immigration maze.