In the stately Mansfield room, where Democrats meet for their weekly caucus lunch just off the Senate floor, Sen. Mary Landrieu (D-LA), appeared this morning alongside Sen. Tom Harkin (D-IA) and a number of entrepreneurs from around the country, at an event dedicated to the idea that health care reform is crucial to the survival of small businesses in America.

It was at once fitting and unusual for Landrieu to appear at this pro-reform event. On the one hand, as chair of the Small Business Committee, how could she miss it. But on the other, she's one of a handful of conservative Democrats openly suggesting she might support a Republican health care filibuster, particularly if the public option in the Senate bill isn't affixed to some sort of trigger mechanism.

About nine minutes in Landrieu channeled her inner Democrat. "While we may not yet completely agree on all of the specific details," Landrieu said, "one thing we can all agree on is doing nothing is not an option."

A breakthrough? A signal that she'd been won over by a majority of senators and the vast majority in her caucus who support the reform effort? Sadly, she didn't want to stick around to clarify. Moments before the Q&A session was set to begin, Landrieu slunk out the side door, leaving Harkin at the podium with the dozens of assembled guests.

Before he fielded his first inquiry, though, most of the reporters in the room had already bolted, and were running down the hallway to catch up with the Louisiana senator before she'd reached the elevators down to the Capitol subway and the safety of her office.

As it turns out, she's not actually ready to commit to giving the bill an up or down vote. "That's the goal of this, is to give people more affordable choices, not just one, you know, government subsidized program, but more affordable choices in the private sector," Landrieu said

The public option proposals in both the House and the Senate would actually be prevented from receiving a government subsidy. But no matter. Landrieu supports Sen. Olympia Snowe's proposal to trigger a public option as a fall back if private insurance doesn't succeed at lowering premiums without public competition. Liberals in both chambers deplore that compromise, and count it a great victory that Harry Reid eschewed it when he put the Senate bill together. But Landrieu says, "I wouldn't count it out."

This exchange highlights the uncomfortable position conservative Democrats find themselves in as health care bills makes in both chambers approach the floor. The different public options in each proposal have already been substantially watered down, and, though conservative Dems remain skeptical of the idea, they may find themselves faced with the question of whether the inclusion of a small measure, extremely popular with the Democratic base, is worth tanking the entire, months long effort.

I asked Landrieu whether she can imagine going from "doing nothing is not an option" to voting to filibuster the final bill. "I can imagine fighting hard for what those people in there want," she said, "which is many affordable choices."