All Democratic eyes will be on Sen. Jeff Bingaman (D-N.M.) at the Finance Committee health care reform markup on Tuesday, when stakeholders expect the normally low-key lawmaker to play a pivotal role in revising Chairman Max Baucus’ (D-Mont.) $856 billion reform blueprint.

Bingaman was a member of the bipartisan gang of six tasked with negotiating Baucus’ health care mark ahead of its debut last week, and health care lobbyists say he could influence dramatically how his 12 Democratic Finance panel colleagues vote on any changes to the chairman’s mark.

“He’s very important … an important validator for other [Democrats] on amendments,— a lobbyist wrote in an e-mail. “If [Sen. Jay] Rockefeller [D-W.Va.] stays off the reservation, they obviously don’t have votes to give unless they pick up [Republicans].—

“Let’s put it this way, if [Baucus] loses Bingaman, he’s got bigger problems with other [Democrats],— the lobbyist added.

Following Baucus’ unveiling of his health care blueprint last week, Rockefeller, another Finance member, immediately criticized it for not including a public insurance option. Although Rockefeller was soothed later by President Barack Obama during a White House meeting, it remains uncertain whether the Mountain State lawmaker will settle ultimately for Baucus’ public option compromise: health care co-ops.

In a statement last week, Rockefeller said co-ops are “untested and unsubstantiated — and should not be considered as a national model for health insurance.—

Without Rockefeller’s support, Democrats have a two-vote margin on the Finance panel.

In contrast, another health care lobbyist said that although Bingaman has been a vocal proponent of the public option, he is expected to shelve his demands for the sake of a deal.

Bingaman hails from the fourth poorest state in the country — where roughly 20 percent of the population lives in poverty — and as a result, the lobbyist said Bingaman will agree to Baucus’ plan because New Mexico’s “health care system is near collapse.—

“The public option is not his deal,— the lobbyist said. “He’s for it, but at the end of the day he’ll be the last guy who champions it. He wants something to happen.—

A mild-mannered lawmaker known to aides as “Jeff,— Bingaman shuns the limelight and declined to be interviewed for this article. Despite his liberal voting record, however, he is considered a moderate on many issues, particularly those before the Finance Committee. According to one lobbyist, Bingaman is considered the panel’s “heart and soul— ideologically among Democrats.

On his ideological left? Sens. Charles Schumer (D-N.Y.), John Kerry (D-Mass.) and Rockefeller. To his right: Baucus and Sen. Kent Conrad (D-N.D.). And despite his apparent lack of media savvy in this summer’s gang of six negotiations, Bingaman was considered to be an influential participant during the months of talks.

“He’s in the middle on the Democratic side,— the lobbyist said. “He’s not a liberal like Schumer, Kerry and Rockefeller — and not [conservative] like Conrad or Baucus.—

“Everyone has been quoting everybody except him,— the source added. “Anything that’s decent in that bill was Bingaman and [Sen. Olympia] Snowe [R-Maine] … it wasn’t Baucus or Conrad.—

The gang of six included Baucus, Bingaman, Conrad, Snowe and Sens. Chuck Grassley (R-Iowa) and Mike Enzi (R-Wyo).

In 2008, Bingaman voted with his caucus 99 percent of the time and received a 50 percent voting score from the U.S. Chamber of Commerce.

Another lobbyist said Bingaman’s low public profile belies his influence on Finance panel Democrats, particularly among liberals on health care issues.

“It matters to them whether he supports [a proposal] or not,— the lobbyist said. “His role in the health care debate has been one where the more progressive, liberal Democrats trust him — even if they may come to a different result, they know Jeff has taken the time to learn the issue. He’s filling some of the void left with Ted Kennedy leaving.—

Another lobbyist downplayed Bingaman’s possible role in Tuesday’s markup, arguing that Tuesday will be Baucus’ show. The Land of Enchantment’s senior Senator and the other 12 Finance Democrats, the lobbyist said, will fall in line.

“You’re not going to find three Democrats who are willing to buck the chairman,— the lobbyist said. “Baucus is in control of this committee on the Democratic side.—

“Everyone is saying their piece [publicly], but in private meetings Senate Finance Committee Democrats are telling Baucus they’re on board,— the lobbyist continued. “The politics are way too big on this. It’s bigger than these individual Senators.—