With the committee expected to spend at least three weeks on the legislation, Republican critics could offer hundreds of amendments to try to reshape the overhaul. They include proposals that could lengthen the timeline for a pathway to citizenship and that could tamper with an already fragile deal negotiated between business and labor groups for a guest worker program. Anticipating an onslaught, Democrats are preparing a robust defense in an effort to keep the legislation largely intact. …

“They’ll be looking to throw obstacles in the way of the process and propose poison pills in order to frame the debate for the far right,” said Frank Sharry, the executive director of America’s Voice, a pro-immigration group, referring to some of the potential Republican amendments. “What they’re really doing is playing towards conservatives, trying to make Marco Rubio and other Republicans uncomfortable, and mobilizing grass-roots opposition.”

Senator Jeff Sessions, Republican of Alabama and a member of the committee, has long been a vocal opponent of the immigration overhaul, and he signaled last week that he planned to try to slow down the legislation’s progress by offering amendments that would “confront the fundamentals of the bill.”