Thanks for the link to that article. I suspected as much. Two key lessons in "Politics 101". 1. The folks screaming the loudest that they are a party's base...usually aren't. If your politicians "aren't listening to you", it is probably because you aren't the majority. 2. Congressional political races are local. You may hate Olympia Snow, Susan Collins and John McCain...but their constituents (read voters) don't. They all have among the highest job approval ratings among their own voters in the country.
We will find out how unhappy the voters are with the Senate's immigration plan. It is worth noting that the three of the four Dems up for reelection this year voted against the bill. The House bill was passed with a sizeable majority including many Dems.