Washington ? In the wake of this week’s massive demonstrations, many House Republicans are worried that a tough, anti-illegal-immigration bill they thought would please their political base has earned them little benefit while becoming a lightning rod for the fast-growing national movement for immigrant rights.

House Republicans rushed through legislation just before Christmas that would build hundreds of miles of fence along the U.S.-Mexico border, mandate that businesses verify the legality of all employees through a national database, fortify border patrols and declare illegal immigrants and those who help them to be felons. After more lenient legislation failed in the Senate last week, the House-passed version burst into public this week, as hundreds of thousands of protesters nationwide turned out to denounce the bill.

Tuesday, House Speaker Dennis Hastert, R-Ill., and Senate Majority Leader Bill Frist, R-Tenn., issued a joint statement seeking to deflect blame for the harshest provisions of the House bill on the Democrats, who they said showed a lack of compassion. “It remains our intent to produce a strong border security bill that will not make unlawful presence in the United States a felony,” Hastert and Frist said.

House Democrats acknowledged they helped block Republican efforts on the floor last December to soften the Republican-crafted section declaring illegal immigrants to be felons, but they said ultimate responsibility for the bill rests with the Republicans, who voted overwhelmingly for its passage.

Tuesday’s maneuvering underscores how the issue has mushroomed into a fierce political debate with potentially large political stakes.

“There was political calculation that they could make this the wedge issue of 2006 and 2008, but it’s not playing out that way,” said Rep. Raul Grijalva, D-Ariz. “This has galvanized and energized the Latino community like no other issue I have seen in two decades, and that’s going to have electoral consequences.”