For the right, talk radio is often a usually good barometer to measure how an issue plays with their base. For many hardcore rightists, the only words they believe are what Rush Limbaugh and his ilk say. They are their trusted sources of information, and like lemmings they do their bidding by raising money, making money, and calling people (as well as sending e-mails, man do they like sending e-mails with cut and paste talking points!). But the downside of this is that con talk radio does not often represent mass opinion. It is a medium representing a fringe or extremist point of view on many issues that aren't shared in the rest of America. On immigration reform, Republicans are now largely convinced that talk radio represents real outrage, but I highly doubt it does - and there certainly isn't a significant liberal pushback to that since our caucus is not as kneejerk xenophobic or racist as the right is.
It reminds me a lot of what happened with Terri Schiavo when the MSM took their usual cues from talk radio and insisted that the nation was "divided" on the issue. If Rush Limbaugh said it, it had to be true, right? No.