4:41 p.m.: Chambliss suggests that "getting information out of this administration has been like having a root canal."

4:36 p.m.: Saxby Chambliss of Georgia arrives. He is the fifth senator to make an appearance in what has become more of a time-limit-free, non-contentious debate than a filibuster.

4:34 p.m.: Citing the Guardian's Glenn Greenwald, Paul suggests that approving of one president's exceptional ability to order drone strikes implies approval of all future presidents' ability to do so.

4:32 p.m.: Even in D.C., the filibuster isn't making much of a dent on Twitter, according to Trendsmap.

4:25 p.m.: Rubio asks that senators stand together when one is demanding an answer from a president. He suggests that a timely, complete answer from the administration on drones would have made today's action unnecessary, adding that confirmation votes are an appropriate time at which to raise issues.

4:21 p.m.: It's pretty easy to envision Paul turning to Rubio during a 2016 presidential debate and saying, "I was pleased when the Senator joined my filibuster." This moment could be on the brink of turning into a much broader media opportunity, if that hasn't already happened.

4:17 p.m.: Florida Senator Marco Rubio now appears. He leads with a joke about having water on-hand. Unnecessary; Paul's ability to speak for hours with very little water has already been demonstrated.

4:14 p.m.: Wyden steps away from the proceedings, suggesting that he hoped more information would be declassified and that he would work to ensure that the larger debate continues.

4:08 p.m.: On Twitter, "Senate" is trending in the United States. Neither "Rand Paul" nor "filibuster" is.

3:59 p.m.: We're at the four hour, 15 minute mark of the filibuster. You can see its current length with this handy ticker, via Matthew Keys. Or, if you're in a hurry: IsRandPaulStillTalking.com.

3:53 p.m.: Wyden arrives. He notes his vote for Brennan in the Judiciary Committee, suggests that the committee on the whole thinks Brennan has the required attributes to lead the Agency. However, he joins Paul's push for more information on the government's drone program, asking for greater checks-and-balances. (Wyden and Paul have been allies on this issue before.)

3:50 p.m.: Cruz continues his Alamo analogy, reading a letter in which defender William Barret Travis called for reinforcements in his doomed final stand.

Today, in bad omens for Rand Paul. RT @chadpergram: Sen Ted Cruz (R-TX) likens Rand Paul's filibuster to the stand at The Alamo. — David A. Graham (@GrahamDavidA) March 6, 2013

3:47 p.m.: Actually surprising news: Oregon's Democratic senator Ron Wyden indicates that he will join the debate on the Senate floor.

!!! RT @ronwyden: Heading to the floor to speak on Congressional oversight of executive branch & rules for targeted killings. — Lachlan Markay (@lachlan) March 6, 2013

3:42 p.m.: Cruz notes that today is the 177th anniversary of the fall of the Alamo. (It is!) On behalf of 26 million Texans, Cruz says, the state is proud that Paul, a native of the state, is standing up for liberty. Cruz suggests that those who died that day would approve of Paul's fight.