Today’s the day.

Early this afternoon, the United States Senate will hold a procedural vote with huge implications for two measures that student and youth activists have been organizing around for a decade — the DREAM Act and the repeal of Don’t Ask Don’t Tell.

In order to overcome a planned filibuster, the bills will need the support of sixty Senators. With only fifty-nine Democrats in the Senate, supporters will need at least one — and possibly more — Republican to break ranks and vote yea.

Both measures have received Republican support before, but party pressure to vote no is extraordinarily high — Democratic voters are frustrated and demoralized heading into this November’s midterm elections, but victories on DADT and DREAM would galvanize the liberal base in a way that could prove devastating to the GOP.

And so, one by one, past Republican supporters of the measures have lined up to announce that they will be voting no this time. Some have indicated that they may be willing to cut a deal, though, and others have so far kept quiet about their plans.

The New York Times today called the DREAM Act’s chances “slim,” but it did so in an article that noted that student mobilization around the bill has already rocked Washington DC. As for Don’t Ask Don’t Tell, the website Politico says that many wrote it off as a “lost cause” last week, but that its momentum seems to be building now.

You can get up-to-the-minute organizing news about the two bills on Twitter at #DREAMact and #DADT. I’ll be updating this post with new news as the day goes on.

11:15 am | Senator Susan Collins of Maine, a key Republican moderate, has said she will vote against allowing DADT repeal to come to the Senate floor under the current rules for debate and amendment.

11:55 am | Senator Scott Brown of Massachusetts is on the floor of the Senate now saying that he will vote no. With Collins and her Maine colleague Olympia Snowe on record in opposition as the rules now stand, it appears that the Republicans will be standing united. Barring a last-minute deal with the Democratic leadership, it looks like the effort to bring DADT and the DREAM Act to the floor this afternoon will fail.

12:35 pm | The Senate just went into recess. They’ll return for the vote at 2:15 pm.

3:45 pm | The motion to bring the bill to the floor failed in a 56-43 vote. I’ve got a new post up here explaining what happened and why.