Kyle Simmons, Senate Minority Leader Mitch McConnell’s (R) longtime chief of staff, plans to launch a bipartisan lobbying shop with a trio of former Senate chiefs of staff, according to a source familiar with Simmons’ efforts.

Simmons is leaving the office next week after 15 years with the Kentucky lawmaker to pursue “opportunities outside of government,” according to McConnell’s office.

He declined to comment further regarding his future employment.

Bob Russell and Tom Ingram, former top aides to Sens. Mark Pryor (D-Ark.) and Lamar Alexander (R-Tenn.), respectively, are expected to join Simmons. Bernie Toon, a lobbyist at the Bechtel Group and former chief of staff to Sen. Jeff Bingaman (D-N.M.), is also said to be joining the firm.

Toon did not return a call. Ingram was unavailable for comment.

Simmons, Russell and Ingram all face a one-year ban from lobbying the Senate because their individual salaries were more than 75 percent of the Members’ they worked for, according to LegiStorm, a Web site that tracks Congressional salaries.

Still, the former chiefs are expected to draw corporate clients looking for political strategy, according to lobbyists.

Simmons is well-known for his political muscle. Ingram and Russell are co-founders of the bipartisan Senate Chiefs of Staff group, which includes most of the Senate’s 100 chiefs of staff.

Ingram has already gotten a head start on shilling for clients. He has been doing strategic consulting for corporate clients, according to press reports.

While the group is giving up the prospect of lucrative salaries at established firms, they will likely make more money after the startup of the firm. Headhunters said Simmons, Russell and Ingram could bring in salary packages of more than $250,000.

“Bipartisan groups of chiefs of staff going into business for themselves is a good model,” said McCormick Group’s Ivan Adler. “What they give up is the security of a steady paycheck that they get at a big law firm or lobbying shop.”

The former chiefs of staff are not heading into uncharted territory. Bob Van Heuvelen, former chief of staff to Sen. Kent Conrad (D-N.D), and John Easton, former chief of staff to then-Sen. Gordon Smith (R-Ore.), have a similar model.

Founded in 2007, VH Strategies brought in nearly $1.5 million, according to the Center for Responsive Politics.

Republicans said Simmons’ departure would likely force a significant shake-up not only within McConnell’s office but the Republican Conference itself.

Sharon Soderstrom, who serves as McConnell’s deputy chief of staff, will take over for Simmons. Soderstrom, who has served as a senior legislative aide to McConnell and former Majority Leader Bill Frist (R-Tenn.), is considered a top policy expert and vote counter, and at least on those fronts, little is expected to change for Senate Republicans.

Less clear is whether Soderstrom will be able to take over the role of McConnell’s muscle and chief internal lobbyist.

One GOP Senator noted that Simmons has been one of the driving forces behind McConnell’s effort to keep his Conference together and on message.

Rather than rely on threats or other traditional forms of arm twisting, Simmons employed what one source called a “finesse” approach to enforcing discipline within the Conference, leaning on his personal relationships to bring along reluctant Members. The ability to maintain message discipline has been key to McConnell’s success, particularly over the past year, and Republicans acknowledged there is no clear successor.

“I don’t know who will fill the muscle role. He had a soft touch,” the Republican Senator acknowledged.

Republicans said Simmons was one of McConnell’s most trusted advisers on communications issues and had developed an acute sense for how Republicans could frame issues to their benefit.

Simmons’ departure is similar to that of Susan McCue, Majority Leader Harry Reid’s (D-Nev.) former chief of staff, in 2006. Like Simmons, McCue’s personal relationship not only with Reid but with members of the Conference gave her the ability to work directly with lawmakers and act as Reid’s cajoler-in-chief.

Republicans said they expected McConnell’s office — and the entire Conference — to take a more “by committee” approach to the political aspects of Simmons’ job. That, aides said, will mean McConnell’s individual policy aides will be more heavily involved in working to keep Senators together on their issues, while McConnell will likely rely on leadership and other lawmakers close to the GOP leader to enforce party discipline.

“Everyone else’s job just got that much more difficult, because Kyle was a man of many talents,” a senior GOP leadership aide said.

Simmons was previously a lobbyist at the firm Quinn Gillespie.