House Majority Whip Roy Blunt (R-Mo.) and his Senate counterpart, Mitch McConnell (R-Ky.), have been forging a closer working relationship in the past several months. But on Thursday they’re taking it to a new level, inviting 200 lobbyists, two Senate leaders and a collection of 50 Congressional and administration aides to a strategy session.

Blunt and his whip team will convene a meeting at 9 a.m. Thursday in Room HC-5 of the Capitol for an hourlong, bicameral agenda-setting confab.

Senate Majority Bill Leader Frist (R-Tenn.) and Conference Chairman Rick Santorum (R-Pa.) will speak, as will McConnell, about issues on their side of the Capitol, while Blunt and House Conference Chairwoman Deborah Pryce (R-Ohio) will give the House’s perspective.

“This meeting on Thursday is the going-public for Majority Whip Blunt and Whip McConnell on the effort they’ve been involved in for the past year and a half to make sure the two bodies are working closely together on major legislative agenda items,” said Gregg Hartley, Blunt’s former chief of staff, now a lobbyist with Cassidy and Associates. “They will specifically be asking the folks on K Street who have worked with them closely in the past to support this effort by engaging their grass roots and grass tops and generating intelligence.”

In addition to Hartley, other lobbyists who were invited or planned to attend include Quinn Gillespie and Associates’ Marc Lampkin and Terry Holt; Nick Calio, who heads global government affairs for Citigroup; Tim McKone, senior vice president of federal relations for SBC Communications; Bruce Mehlman of Mehlman Vogel Castagnetti; and scores of other in-house, trade association and for-hire advocates.

But lobbyists who aren’t on the invite list need not waste their time trying to slip in the door. A House leadership aide said the event is strictly by invitation only, and staffers will check identification. And, of course, there will be no journalists or cameras allowed.

This aide said the event is the first organized “coalitions” meeting to combine representatives of both sides of the Capitol alongside K Streeters.

“This is the first time we’ve worked with the Senate in such an overt way,” said this House leadership aide. “It’s the first time we’ve had the big three coming over to the House side of the Capitol” for a coalitions meeting.

Lobbyists have played a key role in the House Whip organization for years.

“They are really an extension of the whip team,” said Rep. Mike Rogers (R-Mich.), who heads up coalitions and outreach efforts in the House. “Through Roy’s leadership, we’ve been able to take this to the next level.”

Blunt Press Secretary Jessica Boulanger added, “When we work with our allies in the business community, we are able to increase the abilities of our whip team exponentially.”

Lampkin said that from the lobbyists’ perspective, working closely with the whip operation “invests the lobbyists in their agenda, and vise versa. And helps their ability to grow the vote. It means the ability to move bills is more successful.”

For their part, Senate Republican leaders view Thursday’s meeting as a continuation of the ongoing efforts to get the two chambers’ leadership teams working in sync, partly by information-sharing and partly by relationship-building.

While Blunt’s office worked to put together this meeting with the lobbyists, it’s just one of a series of recent actions taken to continue building those relationships, aides say.

Last Tuesday, Blunt attended the weekly whip meeting in McConnell’s Capitol office — a favor McConnell returned that evening by attending Blunt’s weekly whip meeting.

House Majority Leader Tom DeLay (R-Texas) has been attending the weekly Tuesday luncheons of Senate Republicans, and for at least the past three weekly meetings of the House Republican Conference a member of Senate leadership has attended, including Santorum and Conference Vice Chairwoman Kay Bailey Hutchison (R-Texas).

“It’s been a fairly routine deal and it’s worked well,” said Greg Crist, spokesman for Pryce.

GOP aides say the most public outgrowth of this effort will occur at a joint House-Senate leadership press event next week, part of the effort to build support for President Bush’s plan to overhaul Social Security.

Organizers and participants say the Thursday meeting is most likely to focus on broad concepts rather than the nitty-gritty of policies, but issues likely to pop up on the agenda include Social Security reform, energy legislation, medical malpractice, filibuster rules in the Senate and trade agreements.

Some lobbyists involved in the coalitions effort said the House whip organization is serving as a model, given its well-oiled outreach machine on K Street.

“The Senate has always had a more difficult time of integrating with the outside groups,” said one Republican lobbyist. “You hear this all the time, that the House does things, and they die in the Senate. This is an attempt to get in front of that, to set a joint agenda and to work together in a more coordinated fashion with the outside guys.”

A handful of lobbyists who are well-connected in Senate Republican leadership said they hadn’t been invited and did not plan to attend.

Senate Republicans do have their own outreach effort to K Street, with responsibilities divided among three senior Senators. Santorum is responsible for coordinating regular meetings with lobbyists who work for firms, while Hutchison works with trade association lobbyists and Sen. Gordon Smith (R-Ore.) works with in-house lobbyists for corporations and major companies.

Aides and lobbyists said that at Thursday’s session Blunt plans to talk about increased cooperation and lessons from recent victories such as class action and bankruptcy reform and from past bills such as trade agreements with Singapore and Chile and the FSC-ETI corporate tax bill.

“I think it’s a great opportunity to share information about the agenda on each side of the Capitol, the House and Senate side, so everybody can be working together for a common goal on particular pieces of legislation,” said Drew Maloney, a lobbyist with the Federalist Group, who plans to attend the meeting.

Rogers added, “This isn’t about arm-twisting. It’s about communication. It sends a very powerful message that the leaders of the Senate are working with the leaders of the House.”