Accompanying FairVote's 2012 Presidential Election Night Scorecard, we have a scorecard for predicting which party is likely to come out ahead in the national congressional vote based on early results this election night. Using the partisanship data from FairVote's Monopoly Politics 2012 report, you'll be able to impress all your fellow election-watchers with your ability to anticipate a national vote advantage for one party or pick winners in some later-reporting states after the results of only a few races have been announced.

This analysis is a little more complicated than the presidential race evaluation, especially with information from just a few races available, but we believe it is useful - and will be increasingly reliable when you look at returns from more and more House races.

Here's how it works. As a start, it's important to understand district partisanship. Monopoly Politics 2012's analysis assumes that the United States is currently, and has been for several years, split roughly 50-50 on partisan lines. That was the analytic insight we used for our original Monopoly Politics 1997 report that became the basis for Charlie Cook's partisan voting index, which is grounded in the same approach.

For our current analysis of the partisanship of each House district, we compare how well President Barack Obama and his Republican challenger John McCain performed in that district in the 2008 presidential campaign compared to their national percentages of the vote. That measure provides the baseline for judging how congressional candidates are likely to do in a district. As an example of how partisanship matters, consider that all 139 Democratic incumbents in 2010 won in districts where Obama in 2008 had run more than 4% ahead of his national average. Of the 52 Democratic incumbents unseated by Republicans in 2010, 40 were from districts in which Obama had run behind his average.

In 2002, for another example, we estimate that Republicans on average had a national advantage of about 52%-48% meaning that their candidates on average ran about 2% ahead of what they would have earned in a 50-50 year. More specifically, Republican candidates would be generally likely to outperform their district's partisanship, and Republican incumbents that year ran 8% ahead of district partisanship--while Democratic incumbents ran just 4% ahead of partisanship. Due to the many advantages held by incumbents, they on average tend to run about 5%-7% ahead of their district partisanship depending on the year -- see our past analysis of "incumbency bumps," including data on the 2002 election.)

Below, we've identified six open seat congressional races and eight incumbent races from the states where the polls close the earliest: Georgia, South Carolina, Indiana, Kentucky, Vermont, and Virginia. Here's how you can use the charts:

• In open seats, simply see which party is running ahead of the district's partisanship. If you see a trend toward one party "beating the spread" (e.g., winning vote percentages ahead of their party's partisanship in the district) then that party probably will have a national advantage in most districts across the nation.
• In incumbent races, compare how each party's incumbents are doing relative to their district partisanship. If one party's incumbents are "beating the spread" by more than the other party's incumbents, then that's another clear indicator of their advantage in this election.

Finally, for anticipating outcomes in races in general, look at the extent to which partisanship is governing vote patterns. The less of an incumbency bump there is in general, the harder it will be for vulnerable incumbents to survive if running in the other party's turf. The more hard-wired partisanship seems to be for determining outcomes, the more incumbents will be safe if running in a district good for their party and the more open seats will likely break toward the party with the partisanship advantage in the district. (For examples of districts to watch, see our post earlier this week on key House races in 2012.)

Filling out the charts: For each race below, mark down the margin of victory (or defeat) of each incumbent and then the difference between that margin and the district's partisanship. Again, if you see trends in favor of one party relative to partisanships in these districts, you can tell that election night will likely be better for that party's candidates in other districts.

OPEN SEAT RACES

RACES WITH INCUMBENTS