Democrats stuck together during more than two hours of bare-knuckles debate to stop the Republicans' efforts, and preserve the system in which people can obtain driver's licenses without proof of immigration status.
The political fighting began as the full Senate was due on a bill by Democrat Peter Wirth to tighten licensing requirements for drivers under age 18. Three Republicans tried to amend that bill with proposals to revoke licenses for illegal immigrants.
Sen. William Sharer, R-Farmington, offered the first proposed change. Wirth said it was "unconstitutional" because it changed the substance of his bill.
A protracted debated followed. It ended with 25 Democrats voting not to allow Sharer's amendment. In doing so, they overruled Lt. Gov. John Sanchez, president of the Senate.
Fourteen Republicans and Democrat Tim Jennings wanted the amendment heard.
Republicans followed that setback with two more attempts to tack the immigrant licensing measure onto Wirth's bill.
Those proposals, by Sens. Clint Harden, R-Clovis, and John Ryan, R-Albuquerque, failed on 25-14, party-line votes.
Sharer argued that granting driver's licenses to illegal immigrants threatens public safety.
Harden said the system also inconveniences the public.
So compromised are New Mexico driver's licenses, Harden said, that a neighboring state will not accept them to board airplanes.
Sen. Eric Griego, D-Albuquerque, countered that issue was not at all about public safety. Rather, he said, "It's about fear."
The economy is weak, immigrants are under siege and polls say revoking driver's licenses from those in the country illegally is a popular political maneuver, Griego said.
Griego said New Mexico's licensing system works well in that it gives police a way to track undocumented immigrants, who will drive with or without a license.
The number of drivers with auto insurance also has increased since the licensing law's implementation, he said.
Another Democrat, Sen. Howie Morales of Silver City, said the terrorist attacks in New York and Washington, D.C., occurred in 2001.
He questioned why the Republicans now were worried about public safety.
The New Mexico Legislature, dominated by Democrats, in 2003 approved the law allowing illegal immigrants to receive driver's licenses. Republicans in 2005 offered bills to overturn the measure, but got nowhere.
Sen. Steven Neville, R-Aztec, said the licensing issue was steeped in politics because former Democratic governor Bill Richardson made it that way. Richardson, intent on running for president, pushed for the licensing law so he could say he had created a humane immigration policy, Neville said.
In the eight years since the law took effect, about 83,000 foreign nationals have received New Mexico driver's licenses.
The state Motor Vehicle Division does not track how many of them are in the country illegally. Overall, about 1.7 million people have New Mexico driver's licenses.
Revoking the licenses of illegal immigrants is a goal of the new Republican governor, Susana Martinez.
Three House Democrats in a committee vote on Saturday blocked a bill that Martinez favored.
Ryan still has a companion measure in the Senate, but its chances look slim, given Monday's opposition from Senate Democrats.