From this:

President Bush's second-term plans to reshape Social Security, immigration laws and other domestic programs are facing a stiff challenge from a group that was reliably accommodating in the president's first four years: congressional Republicans.

After essentially rubber-stamping much of Bush's first-term agenda, many House and Senate Republicans plan to assert themselves more forcefully to put their mark on domestic policy in the new year, according to several lawmakers...

...But the president's most nettlesome intra-party issue in early 2005 may be immigration, lawmakers said. Bush's goal of granting guest-worker status to large numbers of undocumented immigrants is about to collide head-on with House Republicans' push to crack down on illegal immigrants, in part by denying them driver's licenses...

"If the president wants to maintain credibility with House Republicans, he has to be engaged and willing to pass immigration reform that conservatives want," said Rep. Ray LaHood (Ill.), one of 57 House Republicans who voted against the intelligence bill Bush just signed into law. "If he does that, he will build a bridge" that could open the way to far-reaching changes to Social Security, the tax code and other policies, LaHood said. "If he's missing in action on that issue, he's going to have big problems..."