On Wednesday afternoon, the House was forced to indefinitely defer its consideration of the Democrats' bill to extend FISA. By Wednesday evening, leading Senate Republicans and Democrats had agreed to a compromise bill. It was expected that this bill could move quickly and be signed into law.

But it's become clear that things won't move as smoothly as backers of the compromise might have hoped. While the bill cleared the Senate Intelligence Committee yesterday by a strong bipartisan vote of 13-2 (with only liberals Russ Feingold and Ron Wyden voting against), it was only after adoption of a poison-pill amendment which would prohibit intelligence agencies from conducting surveillance of U.S. citizen terrorists without a court order.

Another roadblock has gotten far more attention however: Senator Dodd has decided to use this issue to suck up to the Democratic grassroots who have so far mostly ignored his presidential campaign. In a video that looks like it was shot in Howard Dean's basement, Senator Dodd says he will block the measure through a hold or a filibuster.

A hold is a curious parliamentary device; it doesn't officially exist in Senate rules. Essentially, it's a gentleman's agreement not to move forward with a bill over the strong objection of any member of the Senate. Holds are taken seriously, but lacking a foundation in the rules, they're subject to discussion, negotiation (and pressure) among Senators.

If Dodd is ultimately forced to withdraw his hold, he can turn to the filibuster -- which can be ended by a cloture vote of 60 or more Senators. When the Senate approved the short-term FISA extension in August, it passed by a margin of 60-28. Assuming that no Senators switch from 'yea' to 'nay,' the votes are already there to break Dodd's filibuster. But what if nervous Democrats under pressure from the Netroots vote with Dodd?

Among the 12 Senators not voting in August were a number from conservative states, who might not want to be blamed by the White House for holding up FISA. They include Lamar Alexander, Jim Bunning, Byron Dorgan, Judd Gregg, Tim Johnson, Trent Lott and John McCain. That's potentially eight votes for cloture--presumably the Netroots will have to swing at least that many Democrats to oppose the extension.

Once again, this is shaping up as an issue that divides Democrats and leaves them open to attacks from the base. It's one more example of the politics that result from the pro-security majority that seems to exist in Congress today.