WASHINGTON — Republican opponents of legislation to overhaul the nation’s immigration laws are readying an offensive intended to hijack the newly released bill as the Senate Judiciary Committee on Thursday begins a review that will offer the clearest sign yet of how difficult a path the legislation faces.

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.

For the bipartisan group of eight senators who drafted the legislation and now hope to shepherd it through committee and onto the floor, each amendment is a potential hurdle.

“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.”