Why do Republicans support immigration?

Why do the Republicans (my party) support immigration, don't they realize they are filling up states which are traditionally full of conservative folk that would normally vote Republican with new comers that will almost certainly vote for a Democrat! For example before the m immigration of hispanics CALIFORNIA WAS A CONSERVATIVE STATE!!!!! yet most of this immigration occurred during Republican presidencies? I mean if I was a politician and a politicians main goal is to be elected then filling up important swing states with people who will not vote for you is rather, well stupid! What has happened in California (which keep in mind has the largest number of Electoral votes) is now happening in Nevada, Colorado and Florida(all went democrat). Arizona and even TEXAS (second largest number of electoral votes) could go for the Democrats in 2012! why? - Immigration! Do the Republicans have a political death wish?