Mercury/Clark & Weinstock co-Chairman Vin Weber, center, with new hires Erick Mullen, left, a former Democratic consultant, and former Rep. Denny Rehberg (R-Mont.). (Jeffrey MacMillan/JEFFREY MACMILLAN)

National public affairs firm Mercury and its Washington lobbying unit, Mercury/Clark & Weinstock, are on a mission to diversify.

For a firm known for its ties to national Republican politicians John McCain and Mitt Romney, that means two things: More Democrats, and more state-level lobbying. Both initiatives are part of co-Chairman Vin Weber’s strategy to make the firm more bipartisan and full-service.

Last month, Mercury opened its first outpost in Raleigh, N.C. — its ninth state-based office outside the District — and today plans to announce a trio of new hires to bolster its $7 million-a-year lobbying practice in D.C., which makes up about a third of the firm’s business.

Joining the Washington office are former Rep. Denny Rehberg (R-Mont.) and Democratic consultants Erick Mullen and Karen Hinton, both of whom have deep ties to the Clinton administration and high-level Democratic players in Congress. Rehberg, a six-term congressman, chaired the House appropriations subcommittee on labor, health and human services, and education before losing a Senate bid last November. Mullen was a senior staffer for Sen. Charles E. Schumer (D-N.Y.). Hinton worked for former Housing Secretary Andrew Cuomo during the second Clinton administration.

Although Mercury has prominent Democratic leaders nationally — co-chairman and former Bronx borough president Fernando Ferrer is in the firm’s New York office, and former California Assembly Speaker Fabian Nunez heads its California operations — its Washington federal lobbying roster is predominantly Republican, by a ratio of nearly 3 to 1, according to the Center for Responsive Politics, a research group tracking money in politics.

Weber founded the independent lobby shop, then called Clark & Weinstock, in 1996, before merging and becoming part of the Mercury brand in 2011. Mercury is a part of Omnicom Group, a global advertising, marketing and corporate communications company.

“We’re consciously trying to build out more Democrats,” Weber said. “It is a really important step for us to take. You need a bipartisan balance to do business in Washington.”

The push, Weber said, is not so much an image makeover as it is a “capability enhancement.” But some of the firm’s Republican allegiances are well documented. Weber was a donor and special adviser to Mitt Romney in the 2012 campaign. Ed Kutler, a leading Republican lobbyist, is a managing director at the firm. And two of Mercury’s former strategists, Brian Jones and Steve Schmidt — famously played by Woody Harrelson in the HBO movie “Game Change” about tensions within the McCain camp over vice presidential pick Sarah Palin — were high-level advisers for the Arizona senator’s 2008 presidential run. Both have since left for other public relations firms.

Shift to state-level lobbying

Mercury’s move to expand lobbying at the state level is part of a shift much of the industry is making as major policy fights move from a gridlocked Congress to state governments.

“People are gravitating toward state lobbying because we’ve reached a point where there’s nothing really going on on the Hill,” said Ivan Adler, a headhunter for lawyers and lobbyists at the McCormick Group. “There’s likely not going to be a lot going on this legislative cycle either. So [Mercury] and others are embellishing their shops in state capitals because there’s business there.”

Weber said firm leaders zeroed in on a handful of states to open up shop — Florida in 2009, California in 2010, Pennsylvania in 2011 and North Carolina this year — specifically because they are “big population centers with lots of issues going on.”

As state officials implement state-based health insurance exchanges mandated by the Patient Protection and Affordable Care Act, health care is poised to ignite policymaking debates at the local level for years to come.

“When I first started out, you didn’t get a lot of questions about state-level activity and grass roots,” said Weber, a former Minnesota congressman. “Now there’s not a line between federal and state issues, and every solid public affairs campaign includes both a grass-roots public affairs and lobbying ability.”