While Senate Minority Whip Trent Lott’s (R-Miss.) impending departure will remove one of the chamber’s few bipartisan dealmakers, his resignation also will leave a gaping hole within the often fractious Republican Conference.

Though he is known for his willingness to reach across the aisle when necessary, much of Lott’s success during his 35-year Congressional career has been based on his ability to find personal and political common ground with conservative and moderate Republican colleagues alike and to serve as a bridge between the two factions of his party.

Sen. John Thune (S.D.), Chief Deputy Minority Whip under Lott and one the elder lawmaker’s newest protégés, said that while “there are people in our leadership that will fill that void” left by Lott, it won’t be easy. Lott was “always interested in finding the middle ground” and had unique relationships across the aisle, with House Members and with moderates that allowed the GOP to hold together and even pick up a few Democratic votes when necessary.

“We are really going to have to work together,” Thune said. “It’s a loss and it’s consequential in terms of the impact, but on the other hand, and Lott has said this, no one is indispensable.”

With Lott expected to leave the chamber by the end of this month, Republicans will hold leadership elections Thursday. Current GOP Conference Chairman Jon Kyl (Ariz.) is expected to ascend uncontested to the Whip position, and his chairmanship will be sought by three lawmakers — Sens. Lamar Alexander (Tenn.), Richard Burr (N.C.) and Kay Bailey Hutchison (Texas).

If Hutchison prevails, her post atop the Policy Committee would open up for fellow Texas Sen. John Cornyn to pursue, possibly against Thune. And a Cornyn victory would open up the Conference vice chairman position, which Sen. Jeff Sessions (Ala.) likely would seek.

For all those potential promotions, Republicans and Democrats alike agreed that Lott won’t be replaced easily.

“Trent Lott saw the world of politics a lot differently, certainly,” said Lott’s Democratic counterpart, Majority Whip Dick Durbin (Ill.). “He understands human nature. He’s operational. Everything was always on the table.”

But for all of Lott’s talents, Durbin suggested that Minority Leader Mitch McConnell (Ky.) did little to take full advantage of the Mississippian’s strengths. McConnell and Lott have suffered cracks in their long- standing relationship, highlighted when McConnell privately supported Lott’s rival — Alexander — for Minority Whip in 2006.

“I didn’t feel Sen. McConnell used Sen. Lott effectively at a time when he should have played a bigger role in reaching some agreements,” Durbin said.

Lott had a reputation for making deals with Democrats, but perhaps even more importantly, the veteran Mississippi Senator had a knack for working within his own Republican ranks. Lott had stocked much of his Whip operation with deal-minded Republicans such as Sen. Olympia Snowe (Maine) — a move many viewed as key to helping keep 49 Senators unified in a narrowly divided chamber.

Lott’s reputation for cultivating relationships dates back to his time in the House. In that chamber, Lott took a number of lawmakers under his wing, including Snowe and a fresh-faced then-Rep. Tom DeLay (R-Texas), bringing them up through the ranks, including tapping them as Deputy Whips during his tenure as the House Minority Whip.

Over the years those professional and personal alliances allowed Lott to act as a bridge between the increasingly divisive wings of his own party and positioned him to keep most moderate lawmakers in the fold during key votes, even as centrists were becoming increasingly marginalized during the 1990s and early 2000s.

One Republican aide said Lott brought to the leadership table “a combination of qualities you don’t find in one individual.”

“He did more than any other Senator to unite different Republicans and he often did it out of sight,” this staffer added. “Once there’s that vacuum with him being gone, people will start to realize exactly how much he did.”

With that in mind, it’s unclear whether any remaining or future Senate leaders can fill the same niche for a party that’s clearly in transition. Already speculation is mounting that his departure will translate into a more conservative GOP Conference.

For instance, while Kyl — who has long been associated with the party’s conservative wing — demonstrated his ability to cross ideological lines during this year’s immigration debate, Republicans believe it is unlikely he will act as a public bridge builder like Lott did.

Rather, as one former GOP leadership aide argued, Kyl could end up using surrogates from both sides of the ideological spectrum to maintain party cohesion rather than take on the role himself. “Kyl could be more of a ‘pick his lieutenants’ kind of guy, putting someone out as the bridge” while working in the background with conservatives and moderates, the Republican said.

While he has not taken many strong ideological stands as leader, McConnell is still a conservative, and he predicted that — with or without Lott — the Conference won’t change its leaning.

“We are a conservative party,” McConnell said in an interview. “If you look at the various ratings, most of our Conference is 80 or 100 percent on most of the conservative scores. I think we’ll be philosophically the same as we have been.”

McConnell was one of just a handful of Senators who got a heads-up about Lott’s unexpected resignation, although sources have said other close allies, such as Kyl, learned as many as several days before.

When asked whether he saw Lott’s exit coming, McConnell gave few details, only saying: “I wasn’t totally surprised.”

And while many Republicans believe McConnell may be relieved that Lott is leaving, given talk of an open rivalry between the pair, McConnell said he will miss Lott both as a “great vote counter” as well as on a personal basis, noting that he and his wife, Labor Secretary Elaine Chao, shared a close relationship with Lott and his wife, Tricia.

“You know, some [people] think that we aren’t friends — that’s just not true,” McConnell said. “I think he was just a spectacular Whip. We had a seamless operation. We had an integrated staff, everybody got along and we were headed in the same direction.”

Yet others in the party have remarked that McConnell and Lott approach party strategy differently, most notably in dealing with the Conference’s moderates. After all, it was Lott who secretly began meeting with a group of about 10 Republican Senators and one Democrat — conservative Sen. Ben Nelson (Neb.) — earlier this year to talk through ways to avoid the growing number of filibusters slowing Senate business in 2007.

Yet even with Lott gone from the halls of the Senate, most anticipate his presence still will be felt, especially since he will continue to have close friendships with many powerful Senators. In addition to Kyl, Lott’s close ally Thune likely will remain the Chief Deputy Minority Whip and it is widely rumored that Burr is Lott’s handpicked entrant into the three-way Conference contest.

It remains unclear what traction Burr will have beyond his Senate class of 2004 and other junior conservatives led by Sens. Tom Coburn (Okla.) and Saxby Chambliss (Ga.). Burr is set to square off against Hutchison and Alexander, who lost to Lott about a year ago by just one vote.

While McConnell quietly backed Alexander against Lott in last year’s Whip contest, the Minority Leader said he’s staying out of the latest round of leadership elections: “I’m not going to get into any of these races. It will all be decided relatively quickly, and we’ll move on.”

Hutchison, for her part, is likely to pull the bulk of her support from fellow women and other conservative Senators, while Alexander is likely to win backing from many of the veteran Republicans, including the powerful Sen. Bob Bennett (Utah).

In fact, Bennett’s support is seen by many within the party as a stamp of approval from McConnell — Bennett has long been one of the GOP leader’s closest Senate confidantes and during Conference meetings often acts as McConnell’s consigliere when the leader must officially stay out of a fight.

Personal relationships tend to play the biggest role in how Senators vote in leadership elections, but they also consider how much political and financial help they’ve gotten from the candidates — especially heading into a difficult election year that puts nearly two dozen Republican seats in play.

According to GOP fundraising data obtained by Roll Call, Hutchison has led the three candidates in raising and giving her fellow Senators $340,700 in contributions and another $721,000 for the National Republican Senatorial Committee this cycle. By contrast, Alexander has raised $435,000 for his colleagues and $135,700 for the NRSC, while Burr has raised $258,000 for Senators and another $47,500 for the NRSC.

As for Lott’s presumptive replacement, Kyl has raised $497,000 for his colleagues and another $200,000 for the NRSC.