The clock wound down on the Senate’s immigration talks yesterday, with both parties hoping for a deal but bracing for the fallout if Republicans decide to block Democratic leaders from taking up last year’s bipartisan bill.

Between immigrant-rights groups wary of provisions seen as too punitive and anti-legalization groups leery of any plans seen as amnesty, senators in the bipartisan talks are under tremendous pressure. Even if a deal does emerge, backlash from both sides of the emotional divide over immigration could imperil the Senate’s progress.

Senate Majority Leader Harry Reid (D-Nev.) reiterated yesterday that a procedural vote to take up last year’s immigration bill would occur today. Reid has asked senators to consider last year’s bill, which won 21 GOP votes, as a placeholder and to continue talking even after debate begins.

“If the 21 [sitting] senators who voted for comprehensive immigration reform will not even allow us to bring the matter to the floor at this moment, it will be difficult to explain,” Majority Whip Dick Durbin (D-Ill.) said on the floor.

But few Republicans are ready to begin the process without strong signs that a new agreement will materialize. Several pointed a finger at Democrats for wavering in their support for the particularly contentious elements of the immigration framework, indicating the precarious nature of the talks.

“If some people decide they would rather have a political message and force cloture on the motion to proceed [to last year’s bill], this could go south,” Sen. John Cornyn (Texas), No. 4 in the GOP leadership, said.

Mounting a filibuster on today’s vote would open the GOP to charges of immigration obstructionism, which some Republicans believe contributed to their midterm losses last year. But Minority Whip Trent Lott (R-Miss.) dismissed the potential risk to his party.

“If you get a good product in the end, the procedural votes along the way don’t matter,” Lott said. “I’m not going to be forced into passing a bad bill.”

Several senators, conscious of the long list of sticking points their colleagues still faced late yesterday, are readying alternative immigration proposals in case the negotiations stall. Sen. Dianne Feinstein (D-Calif.), Craig’s partner on the temporary-worker plan dubbed “AgJobs,” said she still intends to push for stand-alone passage of that bipartisan bill.

“AgJobs has to go ahead, and it has to go ahead fast,” Feinstein said. She offered words of caution for Reid as he presses forward with today’s deadline: “He’s pushing very hard, and this is a very big bill, with a lot of serious impacts in terms of public policy.”

Sen. Kay Bailey Hutchison (R-Texas), chairwoman of the GOP Policy Committee, said she and Rep. Mike Pence (R-Ind.) are working on an updated version of their “touchback” immigration compromise that she would offer if the immigration negotiations crumble.

Hutchison and Pence’s plan won support last year for its mandate that illegal immigrants return to their home countries before beginning any formal path to citizenship. Hutchison said she will revise her bill to include a point system for illegal immigrants to earn their way to legality, a new proposal that has gained some GOP support this year.