Seeking to inject some substance into their mission to foster bipartisanship, Sens. Mary Landrieu (D-La.) and Olympia Snowe (R-Maine) are teaming up with a think tank headed by four former Senate Majority Leaders.

After a week in which both parties appeared to retreat to their partisan bunkers following an all-night debate on the Iraq War, both Senators said the fractiousness of Iraq shouldn’t preclude legislative compromises on other issues, such as national security, health care and climate change.

Landrieu and Snowe decided earlier this year to transform the old Centrist Coalition into more of a forum for cross-party negotiations on a variety of issues, but the new Common Ground Coalition they formed has had trouble gaining traction.

“We didn’t want to just meet for the sake of meeting,” Snowe said. “We needed to find a mission.”

Enter the Bipartisan Policy Center, founded in March by former Sens. Howard Baker (R-Tenn.), Tom Daschle (D-S.D.), George Mitchell (D-Maine) and Bob Dole (R-Kan.). The goal of the center, said BPC Senior Adviser Cameron Lynch, is not to eschew party ties, but to “find moments of principled compromise.”

With a budget of $8 million, funded primarily from nonpartisan foundations, the BPC “was a natural fit” to work with the Common Ground Coalition, Landrieu said.

And by working with the BPC, Landrieu and Snowe may gain some powerful allies for their legislative offerings. The BPC doesn’t want to be a run-of-the mill research group, Lynch said. Instead, the founders hope to “capture the academic scholarship of a think tank, but we will advocate for our position,” he explained.

Already, Lynch said recommendations made by the BPC’s National Commission on Energy Policy have been incorporated into a greenhouse gas emissions bill introduced by Senate Energy and Natural Resources Chairman Jeff Bingaman (D-N.M.) and Sen. Arlen Specter (R-Pa.).

Meanwhile, both Senators said their efforts at forging bipartisan compromises have fallen short, largely because of the demands of their own schedules as well as those of other interested Senators.

“This is something we don’t often have the opportunity to be involved in because we become so engulfed in our schedules,” Snowe said.

So rather than asking Members to attend another in a long list of free-form luncheons, the BPC and Common Ground Coalition will be hosting lunches geared toward specific topics. The first, on climate change, is scheduled for July 25. Other agreed upon topics include port security, Iran’s nuclear capabilities, prison reform, chronic disease prevention, and food safety, Lynch said.

Snowe said they were avoiding talking about Iraq because most Senators already have staked out their positions and the issue — as far as Congress is concerned — likely will come to a head in September anyway, when the U.S. commander in Iraq gives his report on the status of the war.