The President needs allies including his own party. When you take a position on immigration that aligns you with the Dems and RINOs against the majority of your own party, you run the risk of losing the support of the base when you need it most. Loyalty begets loyalty.
Then you assume that your polling data presented by your side is accurate. Sorry I don't. I suspect that was why your position was not able to get more then 40 votes in the US Senate.
See you people never read beyond the 1st line. People agree with you on the problem, they do NOT line up nearly as well with you on solutions. When polled on solutions, as always, the American people are all over the board. They want Border Enforcement, they want something done about illegals, but they also do not want to do anything to restrict immigrants. They ethos of a "nation of immigrants" simply runs too deep. So you people look at the numbers and scream "See 55-60-72-86 (what ever the manufactured number is today) agree with US, Illegal Immigration is a problem. WE all agree on that.
However, the picture is not nearly so clear when you start asking people what the solution is. See the problem is your side simply does not listen to any view that does agree with their position. You have that luxury. People in positions of leadership in this country do not. They are the Representatives of ALL the people, not just the "Only strict enforcement is acceptable" crowd.
I also like to remind all the "Poll Conservatives" that CFR, Medicare RX, The Education Bill, Farm Subsides and a whole host of things you loath also poll very well. You don't get to claim "the polls prove us right" only when they happen to agree with you then scream about "Selling out" when the Pols do stuff you disagree with that polls well. If the position is to be dictated by polls, those of you citing polls now have ceded up your right to disagree when the polls go against you. After all, according to you the polls "prove" the correct position on this issue.
However, we are not a Direct Democracy but a Constitutional Republic. You hired them to represent you. Don't like the job they are doing, you can fire them next election. In the interim, just because YOU feel something should be done one way does not give you veto authority over what they do. They represent ALL the people in their district, state or the nation, NOT just those who agree with YOU.