As a coalition of campaign finance groups turns up the heat on the latest Democratic pick for the Federal Election Commission — labor lawyer Robert Lenhard — Republicans are thinking about naming a top aide to Senate Majority Leader Bill Frist (R-Tenn.) to fill a GOP slot at the watchdog agency.

Alex Vogel — a former general counsel to the National Republican Senatorial Committee and currently the chief counsel to the Majority Leader — is the seeming frontrunner to replace GOP Commissioner David Mason, according to multiple sources.

“Vogel, by far, although a relatively new name who was added to the mix of potential nominees, has become the leading contender very quickly,” remarked one source close to the nomination process.

Vogel did not return calls seeking comment on the matter.

Mason, whose term expired in April, has served on the FEC since 1998. He is unlikely to be renominated by the White House, according to Republican sources, who said GOP leaders are looking to inject some fresh blood into the agency.

Mason — a former senior fellow in Congressional Studies at the Heritage Foundation and a longtime Hill aide — is well-regarded within GOP ranks but has often butted heads with members of the campaign finance reform community during his tenure at the FEC.

Late last week, however, the reform community turned its attention to Lenhard, a Democrat who was immediately tarred as an “opponent of the new campaign finance law” by reformers.

Late Thursday, Senate Minority Leader Tom Daschle (D-S.D.) and House Minority Leader Nancy Pelosi (D-Calif.) announced that they were tapping Lenhard — the popular associate general counsel of the American Federation of State, County and Municipal Employees — to fill outgoing Commissioner Scott Thomas’s slot.

Pelosi and Daschle called Lenhard a “respected attorney with broad experience with campaign finance law,” but campaign finance reform advocates were quick to criticize the choice.

“I have a hard time understanding why Senator Daschle, who helped pass McCain-Feingold, would want to put on the commission a dedicated opponent of campaign reform, someone who would use his position not to enforce the law but weaken it,” Sen. John McCain (R-Ariz) said.

In a statement issued Friday afternoon, Common Cause President Chellie Pingree, Democracy 21 President Fred Wertheimer, Trevor Potter, chairman and general counsel of the Campaign Legal Center, and Larry Noble, executive director of the Center for Responsive Politics, asked Daschle and Pelosi to withdraw their proposal and nominate Thomas to serve yet another term.

But numerous friends and colleagues of Lenhard, who has represented the AFSCME for the past 14 years, jumped to the lawyer’s defense. They characterized him as an intelligent, thoughtful man with integrity who will faithfully enforce the law.

Ellen Weintraub, a Democrat and the current chairwoman of the FEC, said she has known Lenhard personally for more than a decade. She described him as a “serious” and “intelligent” man with “integrity” and “good judgment.”

Those attacking him, she said, simply “don’t know Bob.”

“He’ll be a pleasure to work with,” Weintraub added. “I know there’s some concern because of where he’s coming from and what his role has been in the past.”

Weintraub said that simply because he worked for a particular client in the past does not mean he cannot faithfully assume the duties of commissioner.

A Democratic source close to the Congressional leadership called the criticism of Lenhard “unfair” and said it was simply time for Thomas to go.

“Scott’s been there 18 years, and commissioners, as you know, are term-limited,” the source said, adding that “as the new law comes into effect, having someone who’s actually been an active practitioner and has had the experience of having worked in the regulated community” will be an asset to the FEC.

But Lenhard’s critics charge that he will simply push the labor community’s agenda.

“I’m opposed to the appointment because he’s coming from the segment of the regulated community that disagrees with the new law,” explained Noble, who previously served as the general counsel of the FEC. “He signed the briefs to the lower court arguing that the new law is unconstitutional. This represents the final and complete takeover of the FEC by the regulated community.”

But Lenhard takes exception to that characterization of his actions.

“It’s undeserved,” Lenhard said of the bashing he has received.

“I think they’re making far too much of it,” he added. “It is true: I was ‘of counsel’ to the AFL-CIO at the trial court level and the litigation over the constitutionality of McCain-Feingold.”

Nonetheless, Lenhard maintains that his work was a “far cry from trying to attack McCain-Feingold wholesale.”

Lenhard said he thinks he brings a “good background to the agency.”

“I have a strong background both in the operation of the [Federal Election Campaign Act] and how organizations and individuals who want to be politically active interact and comply with the law,” he explained. “I have a lot of experience dealing with grassroots groups and grassroots activism … I think all of that will be a benefit to the agency.”

Outgoing commissioner Thomas, who began his career at the agency in 1972 as an intern and has served as a commissioner since 1986, seemed less troubled by the decision.

Several sources said Thomas had phoned Lenhard Friday morning to talk about the matter and was very kind and cordial to his likely successor.

As for the timing of the new appointments, that will largely depend on the White House — which must make the actual nominations — and how quickly Republicans decide on a candidate for their open slot.

“There’s a magic pair,” explained one GOP leadership source. “Moving one [nominee at a time] is damn near impossible.”