ABC News has learned that President Obama will be meeting with 16 Democratic senators (and one "Independent Democrat") this afternoon at the White House.

They are: Senators Mark Pryor and Blanche Lincoln of Arkansas, Mark Warner of Virginia, Jeanne Shaheen of New Hampshire, Mary Landrieu of Louisiana, Evan Bayh of Indiana, Claire McCaskill of Missouri, Tom Carper of Delaware, Arlen Specter of Pennsylvania, Mark Begich of Alaska, Mark Udall and Michael Bennet of Colorado, Ben Nelson of Nebraska, Bill Nelson of Florida, Kay Hagan of North Carolina, Herb Kohl of Wisconsin, and Independent Democrat Joe Lieberman of Connecticut.

The meeting is scheduled for 4:15 pm ET, in the Cabinet Room.

Many of these senators have expressed concern about if not downright opposition to key elements of President Obama's health care proposals, particularly his push for a government-run public health care option to compete with private insurers to drive down costs.

[T]he time has come--and in fact, it is long overdue--for them to begin forcefully making the case that being a member in good standing of the party’s Senate caucus means supporting cloture motions on key legislation even if a given senator intends to vote against it.

This case was, in fact, briefly made in July by Senate Democratic Whip Dick Durbin--but it gained little traction. Durbin’s argument should be revived in and outside the Senate. Right now, progressive groups around the country are in the midst of efforts to agitate for a “public option” as an essential feature of health reform, and eventually will devote enormous efforts to support final passage of health reform, if we ever get to that point. Wavering Democrats have been targeted for ads and other communications, with mixed results. A significant fraction of that pressure should be devoted to a very simple message: Democrats should not conspire with Republicans to obstruct a vote in the Senate on the president’s top domestic priority. Vote your conscience, or your understanding of your constituents’ views, Ben Nelson, but don’t prevent a vote.

There are those who would respond to this suggestion by arguing that a senator voting for cloture but against the bill could be accused of flip-flopping or deviousness. Let them provide the evidence that voters understand or care enough about Senate procedures to internalize that charge. When John Kerry got into so much trouble in 2004 by saying that he “actually did vote for the $87 billion before I voted against it,” he was the one trying to explain arcane Senate procedures. “I voted against ObamaCare, but I didn’t try to keep the Senate from voting” should be a pretty easy sell for any Democrat, particularly since the contrary argument requires an explanation of cloture, not exactly a household word.

The harder question is whether public pressure to support one’s party and president on a cloture vote could be supplemented by more tangible sanctions against senators who won’t at least let health reform or other critical legislation get to the floor--such as withholding choice committee assignments or party committee funds. But until Democrats begin to question the right of certain Democratic senators to maintain their tyranny, possible sanctions are beside the point.