5:30 p.m.: The quarantine on exit polls is lifted, so the numbers will start rolling in. You'll probably see leaked exit poll numbers earlier in the day on Drudge, Redstate, Kos, and other sites. Ignore them. The exit poll consortium reports in waves, and the first wave represents a fraction of the vote - usually the smallest fraction, and usually those folks who've voted early in the day. The first and even the second waves of exit poll numbers won't give the full picture for close races. For that, you'll have to wait until the polls close and the networks can combine the third-wave exit polls, for which sample sizes are more than 2000 voters, with data from individual precincts.
7:00 p.m.: Polls close in Florida. If Republicans pick up three or more of the following House seats - FL-02 (Allen Boyd), FL-08 (Alan Grayson), FL-24 (Suzanne Kosmas), and FL-22 (Ron Klein) - they're in great shape for the night and likely to take over the House, particularly if the margins of victory in these races are greater than a few percentage points.
Polls also close in Virginia, where Rep. Tom Perriello is one of the few vulnerable Democratic House members who is not backing down from his alliance with Obama. Democrats will be very interested to see how badly Perriello loses - and they do expect him to lose.
7:30 p.m.: Kentucky's polls close at 6 p.m., and the state counts votes pretty slowly. If the Senate race between Republican Rand Paul and Democrat Jack Conway remains close by 7:30, it means that plenty of Democrats turned out to vote, which means that they managed to prevent a major Republican wave in Kentucky. This would seriously jeopardize the GOP's chances of seizing control of the Senate. Recent polls, however, suggest such that Paul will win easily, leaving the question of Senate control dragging deeper into the night.
On the House front, polls close in North Carolina and Ohio at 7:30. Republicans need at least three pick-ups between the two states to get to their magic number of +39 and win control of the House; if they get more, they're probably looking at an overall gain of 50+ seats. Watch North Carolina's races, in particular: If Democratic Rep. Heath Shuler drops the ball, despite having kept the lead for most of his 11th district race, it will be a real sign of a Republican night.
And in Indiana, if Democrats Joe Donnelly and Baron Hill are shellacked, expect the same for their party at large.
If and when it becomes clear that the Republicans will take over the House, expect President Obama to call presumptive Speaker John Boehner to offer his congratulations and suggest they work to find common ground.
8:00 p.m.: Now, a half-hour after polls close in West Virginia, is the earliest we'll have a real sense of what's going to happen with the Senate. At this point, through a combination of precinct reporting and third-wave exit polls, Democrat Joe Manchin's fate should emerge. If Manchin beats John Raese, GOP control is unlikely.
Also at this hour, two Democratic committee chairs, Missouri's Ike Skelton and Massachusetts' Barney Frank, could be defeated.
9:00 p.m.: The Senate picture comes into focus. If Raese has defeated Manchin in West Virginia and Pat Toomey has a solid margin of victory against Rep. Joe Sestak in Pennsylvania, where polls close at 8, the GOP will have a shot at Senate control.
Republicans are almost certain to pick up four Senate seats: Indiana, where polls close at 6, Arkansas, where polls close at 8:30, and Wisconsin and North Dakota, where polls close at 9.
10:00 p.m.: This will be a good time to check in on the governor's races in Florida, Ohio, and Colorado. Democrats are eager to keep the governor's mansions in these states for 2012 campaigning and redistricting purposes - and they've got a shot to do it. In Ohio, Democrats are also trying to make sure they're well-represented on the state's reapportioning board. We should know about Florida and Ohio, where polls close at 7 and 7:30, well before Colorado, where polls close at 9 and where counting is a bit slower.
Meantime, polls close in Nevada, where the power of the Tea Party will be tested in Sharron Angle's bid to knock off Democrat Harry Reid.
11:00 p.m.: Polls close in California. Victories by Jerry Brown over Meg Whitman for governor and by Barbara Boxer over Carly Fiorina for Senate could make this state one of the rare bright spots for Democrats. Such good news for Dems could be tempered by Patty Murray losing to Dino Rossi in Washington State, where polls also close at this hour but where results will only be provisional until the state collects all of its ballots one week later.
Midnight and beyond: Alaska's polls begin to close. It's unlikely the Miller-Murkowski-McAdams Senate race will decide who controls the upper chamber - by now, it should be clear that Democrats have maintained a slim majority - which is good because we may not know the winner there for a month or more.
As for what it all means: Well, Republicans will claim a mandate while Democrats will point to a faltering economy and the usual midterm losses by an incumbent. And both will be right, partly.
*All times are EDT.