One of the most intriguing aspects of last week’s immigration reform deal might be the emergence of Senate Republican Conference Chairman Jon Kyl (Ariz.), long one of the most ideologically committed conservatives in the Senate and standard-bearer for the movement, as the broker of a major bipartisan agreement on an issue that had split not only the two parties but the GOP itself.

The Senate is expected to begin work on the bill today. The legislation would make sweeping changes to the nation’s immigration and border security laws. As part of the deal, lawmakers included a series of border security and workplace “triggers” that must be met before a new temporary worker visa program can come online and before the estimated 12 million illegal immigrants in the United States can begin the process of naturalization.

For instance, the federal government will first have to put up a series of new electronic and physical fences along the Mexican border, end its “catch and release” program for illegal immigrants, install land-based radar systems on the border to help track illegal immigrants and step up enforcement of rules barring companies from employing illegal workers.

Tasked by Minority Leader Mitch McConnell (R-Ky.) with bringing his fractured party together on immigration, Kyl quickly became the bridge between the White House and Sen. Edward Kennedy (D-Mass.) on the one hand and conservative lawmakers such as Sen. John Cornyn (R-Texas) on the other. His pivotal work in bringing the two sides together won Kyl significant praise from Democrats and Republicans alike.

Senate Minority Whip Trent Lott (R-Miss.) said Kyl’s participation in the talks was “indispensable” to crafting an overall deal.

“He did a marvelous job,” Lott said. “We have a ways to go, but he deserves a lot of credit for pulling together something that appears to be marginally acceptable for Republicans.”

Sen. Dianne Feinstein (Calif.), a key Democratic negotiator, said Kyl was integral to producing a compromise, saying “it’s a very big deal that we got something that even conservatives can support. … He played a real role.”

Sen. Johnny Isakson (R-Ga.), a conservative who opposed immigration reform last year, said Kyl was key to bringing the factions together, saying without his input, many conservative ideals wouldn’t have surfaced in the final product.

“He saw to it that we never crossed the lines to what conservatives are committed to,” Isakson said. “He deserves tremendous credit for not sacrificing principles but at the same time giving every side an opportunity to air their differences.”

Isakson said that all sides “had our bottom lines” and ultimately Senators were able to put aside their differences “without trying to game the process.”

Despite the kind words for Kyl, other Republican conservatives already are on the attack — characterizing the bill as too left-leaning — including Cornyn and Sen. Jim DeMint (S.C.), the chairman of the Steering and Policy Committee. DeMint has called the bill “amnesty” and on Friday asked for a “full debate” on the measure, which he said was too important to “jam into a couple of days” of floor debate.

Likewise, a GOP aide said initial reviews of the agreement already are turning up problems. For instance, the bill appears to not go as far as conservatives had expected in bringing an end to the government’s catch-and-release program, a problem lawmakers almost surely will attempt to fix during this week’s floor debate.

Additionally, throughout the past several months, some GOP lawmakers and conservative activists privately complained that a number of key issues were being kept off the table and expressed concern that Kyl was working too closely with the White House. Conservatives also have argued that Kyl’s work on the bill will give it undeserved legitimacy with some Republicans.

Kyl has rejected those arguments, pointing out that without a strong conservative voice in the room the bill produced would have been much closer to the legislation passed by the Senate last year. For instance, during an interview on Fox’s “Hannity & Colmes” last week, Kyl argued that he decided to participate in the negotiations “because my voters said do something about illegal immigration. I didn’t think I could sit on the sidelines and let Ted Kennedy and other Democratic friends in the Senate write an immigration bill I knew I would hate.”

“This debate is far from over,” said one GOP Senate aide. “While Sen. Kyl has given a modicum of credibility to this initial compromise, there’s a distinct possibility that it will be overtaken once conservative Republicans see what either is or isn’t in this legislation.”

Kyl is certainly not the only conservative on board. Isakson and Sen. Saxby Chambliss (Ga.) — both of whom fought last year’s bill mightily — have gotten behind the deal.

Even National Review editor Rich Lowry, writing on his blog “The Corner,” gave Kyl credit. “I have a tremendous amount of respect for him, as does anyone who knows his work. I think he’s cut a bad deal. But in fairness to him, with a Republican President willing to sign pretty much anything, he didn’t have much leverage and figured if he didn’t engage, something much worse could become law. In short, Bush should be more a target of conservative ire than the Arizona senator,” Lowry wrote.