Editor's note: CNN's "Election Night in America" coverage begins at 7 p.m. ET Tuesday. Ed Rollins, a senior political contributor for CNN, is senior presidential fellow at the Kalikow Center for the Study of the American Presidency at Hofstra University. He is a principal with the Dilenschneider Group, a global public relations firm. He was White House political director for President Ronald Reagan and chairman of the National Republican Congressional Committee.
New York (CNN) -- Even though the American elections won't be decided until the polls close tonight, the Irish bookies late last week started paying off bettors who predicted Republicans would win a majority in the House of Representatives. And they stopped making new bets. That's a pretty definite statement!
Although I am very confident my party (Republican) will win the House, I usually like to wait until the voters have voted before taking any victory laps. Many of my pundit friends have had a field day attempting to analyze, over the last several weeks, the early voting patterns of those of you who have cast ballots already and argue what it all means. I have always been more concerned with the late counting of votes rather than the early voting.
And because so many races are so close, this is one election in which every vote can matter.
There is an old saying in the business: "We only hold elections to see if the pollsters are right!" And if the pollsters are right, it will be a big night for Republicans and a lot of second-guessing at the White House.
Certainly viewers will know some trends and results shortly after the polls close. But in other cases, it will be late Tuesday and maybe even sometime Wednesday before we know the final results -- particularly in the Senate, where key Western races may alter the final outcome.
Here is what's at stake: There are 37 Senate races being contested (19 Democratic and 18 Republican). Fourteen of those seats are open, meaning either the incumbent is not running for re-election or has been defeated in a primary.
In order to win a Senate majority, Republicans have to hold Alaska and all their open seats: New Hampshire, Kentucky, Ohio, Florida, Missouri, Utah and Kansas. And they must win 10 Democratic seats. If any of the Republican seats go to Democrats, the Democrats will continue to hold the majority. Everyone has all but conceded two Democratic open seats: the North Dakota seat will be won by Republican Gov. John Hoeven, and the Indiana open seat is likely to be won by former Sen. Dan Coats, also a Republican.
The most vulnerable Democrats running for re-election are Sens. Blanche Lincoln of Arkansas; Russell Feingold of Wisconsin; and Harry Reid of Nevada, the Senate majority leader. The Nevada election is the most heavily watched race in the country, and it has been neck and neck in the polls.
Reid's opponent is Sharron Angle, a Tea Party-backed candidate and former Republican state legislator. This race has gone back and forth, but Angle took a narrow lead going into the final weekend after surviving millions of dollars of negative advertisements. If she wins, this will be the biggest story of the night.
The next best chances for Republican gains are the Illinois, Pennsylvania and West Virginia open seats. The West Virginia Senate race between Democratic Gov. Joe Manchin and businessman John Raese has been a back-and-forth contest. If Raese upsets the popular governor, Republicans are in the chase to make the Senate very close. Other vulnerable Democrats are Sens. Michael Bennet of Colorado, Patty Murray of Washington and Barbara Boxer of California.
Here is what's happening in the House: All 435 seats are up, and 43 seats are open (20 Democrats and 23 Republicans are not running for re-election). In the present Congress, there are 256 Democrats and 179 Republicans. Two seats are vacant.
CNN has systematically chosen 100 congressional races to focus on. Fifty are viewed as the most competitive. Four of these are Republican and the rest Democratic. They have listed another 50 House races to watch. Five of these are Republican and the rest Democratic. This is a far larger number than in most midterm elections, but all of these races have shown signs they are competitive.
Republicans must win 39 seats to win the majority. If early in the evening, Democratic incumbents start losing in the early returns from states such as New York, Pennsylvania, Ohio and Florida, then it is likely the trend predicted for Republicans to gain a majority in the House will come true.
There are 16 vulnerable seats in those four states and another 11 on the watch list. If at the end of the night you see that either the dean of the House -- John Dingell of Michigan who has been in Congress since 1955 -- or Barney Frank of Massachusetts has lost, then you know it's been a historic election.
That sums up the congressional and Senate races, but many states have other contests, including 37 governors' races (19 Democrats, 17 Republicans and one independent up for election). Twenty-four are open seats. Republicans are expected to easily end up with a majority of governors.
Across the country, there are 6,118 state legislative seats also being contested, along with 160 ballot measures in 37 states.
Tune in for what should be an exciting evening. But most of all, go vote!
The opinions expressed in this commentary are solely those of Ed Rollins.