But the AP also reports that there's frustration in some precincts as voters and election workers adjust to new methods for voting. Problems have been reported from scattered regions throughout the country. Absentee ballots may also play a more pivotal role this year. The Virginia Board of Elections, for instance, reported nearly three times as many absentees this year as in the previous midterm election in 2002.

In just a few hours, we'll know whether this was a national election–which polls indicate probably favors the Democrats–or a race-by-race scenario, in which the Republicans are likely to do better. Democrats need a net gain of 15 seats to take a majority in the House. They need six for Senate control.

Here's what to watch for–and when–after the votes start to roll in tonight:

(We've identified congressional districts using the state postal abbreviation and the district number. All times are Eastern.)

* 6 p.m.:Polls begin to close in Indiana and Kentucky. There are several races on either side of the Ohio River in these two states that could be close. Republicans hold all these seats and are running for re-election. They are: Chris Chocola (IN 2), John Hostettler (IN 8),Mike Sodrel (IN 9), Anne Northup (KY 3), and Geoff Davis (KY 4). Hostettler has badly trailed in polls, but the other four could hang on. If Democrats take a majority of those five, it may be a harbinger of a bad night for the Republicans. There were sporadic reports of malfunctioning machines in Indiana earlier today.

* 7 p.m.: Florida, Georgia, New Hampshire, South Carolina, Vermont, and Virginia close their polls. In the Sunshine State, FL 9 (open), FL 13 (open), FL 16 (open), and FL 22 (Clay Shaw), all Republican-leaning seats, are pivotal. Polls indicate that Republican Rep. Katherine Harris is trailing far behind Democrat Bill Nelson in her quest to oust him from his Senate seat. In Georgia's 8th District, Jim Marshall is one of only a handful of Democratic incumbents facing a stiff GOP challenge. Up north, look for a possibly close race in New Hampshire's 2nd District, now held by Republican Charles Bass. And in Virginia, a competitive Senate race pits incumbent one-term Republican George Allen against Democrat Jim Webb, a Navy secretary in the Reagan administration.

7:30 p.m.:Ohio, North Carolina, and West Virginia shut down. Ohio was the pivotal state in the 2004 presidential race; it could be a bellwether this year for control of Congress. In the Senate race, incumbent Republican Mike DeWine has trailed Democratic Rep. Sherrod Brown in late polls. Were DeWine to pull this one out, the GOP could look for an easy majority in the Senate. The races in the Cincinnati area's 1st and 2nd House districts, as well as Columbus's 15th District, feature threatened Republicans. In the Columbus race, incumbent Deborah Pryce is the fourth-ranking Republican in the House.

In far western North Carolina, many observers are watching the race in which Republican incumbent Charles Taylor faces Heath Shuler, a Democrat and former professional football quarterback. No close races are expected in West Virginia.

8 p.m.: Lots of closings–Alabama, Connecticut, Delaware, D.C., Kansas, Maine, Maryland, Massachusetts, Michigan, Mississippi, Missouri, New Jersey, Oklahoma, Pennsylvania, South Dakota, Tennessee, and Texas. Connecticut's three Republican House members–Rob Simmons (CT 2), Chris Shays (CT 4), and Nancy Johnson (CT 5)–all have their backs to the wall in a state where the president and the Iraq war are unpopular.

Maryland has close statewide races for governor and senator.

Missouri has perhaps the nation's closest Senate race, featuring Republican Sen. Jim Talent and Democrat Claire McCaskill.

In New Jersey, incumbent Democrat Bob Menendez, who was appointed to the seat just a year ago, has run neck-and-neck with Republican challenger Tom Kean Jr.

Across the Delaware River, Pennsylvania Sen. Rick Santorum is in big trouble. Polls show Bob Casey Jr. winning possibly by double digits. And in several House races–three of them in the Philadelphia suburbs–Republicans are fighting vigorous Democratic challengers. The endangered GOP incumbents are Jim Gerlach (PA 6), Curt Weldon (PA 7), Mike Fitzpatrick (PA 8), and Don Sherwood (PA 10). Polls indicate that Sherwood is trailing, and few are betting on Weldon either. But if the other two hold on, party control may not be decided until the wee hours.

In the Tennessee race for an open Senate seat, Republican Bob Corker led Democrat Harold Ford in late polling.

* 9 p.m.: Arizona, Colorado, Louisiana, Michigan, Minnesota, Nebraska, New Mexico, New York, Rhode Island, and Wyoming. The mountain states begin to weigh in. There are at least four possible party turnovers of Republican-held seats in Arizona, Colorado, and New Mexico: J.D. Hayworth (AZ 5), Heather Wilson (NM 1), and the open seats in Arizona's 8th and Colorado's 7th districts.

In New York, polls indicate that Democratic Sen. Hillary Clinton is set to win big, setting the stage for a possible presidential run. Meantime, there are several Republican-held upstate seats that are looking like toss-ups, among them Sue Kelly (NY 19), John Sweeney (NY 20), and an open seat in the 24th District.

In Rhode Island, Republican Sen. Lincoln Chafee has recently shown momentum in polls against Democratic challenger Sheldon Whitehouse.

* 10 p.m.: Idaho, Iowa, Montana, Nevada, North Dakota, Oregon, and Utah.Democrats are knocking on the door in districts scattered throughout these states, including Jon Porter in Nevada's 3rd District and open seats in Idaho's 1st, Iowa's 1st, and Nevada's 2nd.

* 11 p.m.: California, Washington, and Hawaii.The Republicans face stiff challenges to John Doolittle (CA 4), Richard Pombo (CA 11), and Dave Reichert (WA 8). An added variable in the Reichert race was an extraordinarily powerful rainstorm moving across the state. If the House's overall look is still razor-thin at this point, one of these races may determine the outcome.

* Midnight: Alaska.

That's the order in which we expect to see results tonight, but there are two caveats:

• There are no promises about whose vote-counting machinery is most efficient. We may have good results from State A before State B, even if A closes later than B.
• Before the numbers start tumbling in, whether online or on TV, remember one rule of the road: for very incomplete returns, pay absolutely no attention to the raw vote totals unless you are familiar with where the votes were cast. If, for instance, you see returns that show a Democratic candidate winning 90 percent of the vote, that means nothing if the only ballots thus far counted are from inner-city precincts, where a 9-to-1 margin would not be uncommon for a Democrat. Meantime, bloggers will try to provide some context to the raw totals if they know from which precincts or regions the votes are coming.