WASHINGTON (CNN) -- The Senate voted Wednesday for an amendment to the Immigration Bill that would cut the number of guest workers from 400,000 to 200,000.

The measure was the second of two Democratic amendments aimed at drastically altering bipartisan immigration legislation. The first, which would have eliminated the guest worker program entirely, was voted down Tuesday.

The amendment passed on a 74-24 vote.

The Immigration Bill is the result of a deal struck after nearly three months of bipartisan talks and endorsed by the White House last week. It would offer the estimated 12 million undocumented immigrants now in the United States a path to citizenship, boost border controls and establish a guest-worker program that would grant workers a two-year residency.

The bill has drawn criticism from both conservative critics, who see it as "amnesty" for undocumented workers, and liberals, who claim it would limit opportunities for unskilled workers. It has been a source of heated debate since Monday evening, when it came to the floor after being presented Saturday for consideration.