Infighting within the Senate Democratic Caucus has stalled work on the chamber’s energy bill, forcing Majority Leader Harry Reid (D-Nev.) to delay resumption of the immigration debate until the beginning of next week, Reid said Wednesday.

At press time Reid and other Democratic leaders were working to bring an end to a fight between backers of more stringent automotive efficiency rules and Michigan Democratic Sens. Carl Levin and Debbie Stabenow, who are seeking to reduce those levels.

But with progress in the mediation slow, Reid was forced to push back several key votes until next week. In addition to a vote on a motion to proceed to immigration, Reid also was expected to delay a vote to take up legislation that would change the way workers vote on whether to form a union. While that Senate vote is all but certain to fail thanks to united Republican opposition, Reid has promised union leaders he would at least make an attempt to vote on the issue.

One bright spot for both sides could be the cancelation of this weekend’s planned session. A GOP leadership aide said talks had begun on the possibility of finding some way to run the clock down on the 30 hours of debate on the cloture petitions before Friday so Members could break for the weekend.

The internal struggle brought work on the floor largely to a stand-still on Wednesday and prompted gleeful criticism from Republicans.

“The floor’s a mess,” one GOP leadership aide quipped, calling Reid’s handling of the floor schedule a “disaster.” The aide also said it will give Senate Minority Leader Mitch McConnell (R-Ky.) and other leaders several more days to message the union voting bill, which they have attacked for provisions eliminating the secret ballot process. The bill “has really unified Republicans at a time that we could use some unity,” the aide said.

While Reid spokesman Jim Manley acknowledged that the energy negotiations have delayed work on the immigration bill, he argued that Republicans also have contributed to the delay because of disagreements over votes on a number of GOP amendments. “What’s become crystal clear this afternoon is that Republicans are blocking Democratic efforts to pass this bipartisan package.”

Indeed, with conservative outrage at their handling of the immigration bill continuing to roil, the delay in the resumption of the debate could prove problematic for Republican leadership as well.

Despite efforts by McConnell to steer clear of the topic until debate resumes, conservatives both in the Senate and across the country have continued to rail against his decision to back a plan by Reid to tightly limit debate in such a way as to all but preclude amendments by most opponents.

Sen. Jeff Sessions (R-Ala.), one of the most vocal critics of the bill, said the process for considering the bill and leadership’s unwillingness to push for more time for conservative critics to try to amend the bill could lead conservatives in the party to feel disenfranchised. “I think there’s a danger of that perception,” he said, adding that a “decent respect for our constituents means that when they have serious concerns with a piece of our legislation we should back off and address them honestly and openly. This process is not optimal,” Sessions said. “It’s one that increases suspicion and skepticism, not dissipates it.”

Sen. John Cornyn (R-Texas) — who as vice chairman of the Senate Republican Conference is a member of the GOP’s leadership team — also criticized the process. “What I object to most is the lack of transparency and thus the lack of accountability” in how the immigration bill was drafted, Cornyn said. “This isn’t any way to run a railroad. This is not the finest hour in the Senate,” Cornyn added.

Meanwhile, in the House, Democrats began the first in a series of “listening sessions” to prepare for its own immigration debate once the fight shifts out of the Senate.

Although some members of the House Democratic Caucus have indicated a desire to break the bill up into smaller parts, that idea has thus far received a cool response.

House Majority Leader Steny Hoyer (D-Md.) said the Judiciary subcommittee is focused on producing a single measure, but did not rule out the possibility of a series of smaller bills.

“It’s not beyond the realm of possibility we would do that,” Hoyer said, adding later, however, that: “I’m not sure there are advantages” to debating several individual measures.

The Congressional Hispanic Caucus also has indicated it would oppose breaking up the bill.

Jennifer Yachnin contributed to this report.