By now you're probably at least somewhat familiar with the cast of characters in the Senate Democratic caucus--Ben Nelson, Joe Lieberman, etc.--who pop up every time a major Obama agenda item is making its way through the legislative process to say, "not so fast!"

But right now, in the House, a group of Blue Dog Democrats is stifling its own party's health care reform proposal, and, for the most part, Americans don't really know who they are. They might know what a "Blue Dog" is, generally speaking--a conservative Democrat from a Republican district, primarily concerned with shrinking the federal deficit (unless the deficit is created by defense and war spending, or tax cuts for the wealthy) and the well-being of big business.

For their pro-corporate positions, and willingness to throw their weight around Congress, the Blue Dogs are richly rewarded. And this year--with energy, financial, and, yes, health industry interests trying desperately to weaken reform legislation--they're on a record pace. But within the Blue Dog caucus there are a range of personalities and animating forces, and it's worth taking a moment to review who the key players are.

Rep. Mike Ross (D-AR): Though not listed as a Blue Dog caucus leader, Ross has, perhaps more than any other Blue Dog, taken the health care reins out of the hands of party leaders. As a member of the Energy and Commerce committee, Ross led six other committee Democrats in a push to stall the legislation, and they've largely succeeded. The fifth-term congressman is a former small business owner, representing the southern half of Arkansas (not including Little Rock). As a Blue Dog, he's insisting that health care costs decrease, but as a representative of a rural district, he's seeking to increase Medicare reimbursement rates to rural doctors--goals that are in fundamental tension with each other. Often, conservative Democrats insist that they're voting their districts which tilt to the right, but though Ross' district does indeed tilt right, the peculiarities of Arkansas politics mean that he often does not face a Republican opponent.

Rep. Bart Stupak (D-MI): Serving alongside Ross on the Energy and Commerce Committee are six other Blue Dogs--including Reps. Bart Gordon (D-TX), Jim Matheson (D-UT), Charlie Melancon (D-LA), John Barrow (D-GA), Baron Hill (D-IN), and Zack Space (D-OH). Stupak, though, has been an unusually vocal critic of the health care reform process. For him, the key seems to be abortion--specifically, he's seeking to assure that the House health care bill contains a provision ban the use of federal funds for abortion. Stupak recently lost a bid to ban federal funds for abortion in the District of Columbia, and at least part of his intransigence on health care appears to be rooted in frustrations stemming from that defeat.

Rep. Dan Boren (D-OK): Boren is one of the House's most conservative Democrats. He represents the eastern third of Oklahoma, and has since 2005. Last election season he whipped his Republican opponent by a 40 point margin. That might indicate a bit of flexibility--that or that Boren might be able to at least lay low on some issues and vote with his party. But no. Down the line, Boren demonstrates a fealty to big business interests in his state. Concerned with the loss of federal funds (and, perhaps, jobs) in his district, he was a vocal and early opponent of the administration's defense spending overhaul. Along the same lines, he has a weak environmental record. Since being elected, he's received hundreds of thousands of dollars from the oil and gas industry and electric utilities, and, about $200,000 alone from health industry professionals--which may at least partially explain his opposition to swift reform.

Rep. Charlie Melancon (D-LA): Like Boren, Melancon has been a member since early 2005. Unlike Boren, though, Melancon is a member of Blue Dog leadership. And he serves on the House committee--Energy and Commerce--where Blue Dogs are holding health care reform hostage. He was re-elected in 2008 without a Republican opponent and may run for Senate in 2010. He's a one-time small business owner, a Roman Catholic, and bristles at being called a liberal.

Rep. Jim Cooper (D-TN): Given his prominent role helping to kill Clinton care in 1994, it's sort of surprising how small a part he's played in these negotiations. You might say he's the Blue Dog that didn't bark. Except that, today, he sort of did. He said that an agreement on health care reform was still "months away," and criticized Obama for giving Congress too much latitude in drafting reform legislation. "I hope that doesn't turn out to be a mistake." The ironies abound--in 1994, conservative Democrats and Republicans lambasted the White House for just the opposite, charging that one of Clinton's chief mistakes was drafting his reform proposal behind closed doors, when it should've been written by legislators.