When we analyzed the Massachusetts election returns on January 19, we noted the presence of a phenomenon called the “Obama plunge”, which refers to the drop-off in Democratic support since the 2008 Presidential election in major statewide and/or Congressional elections. This drop-off is fueled by an energized conservative base and a significant plunge in Democratic support from independent voters, and has consistently been in the 12-15% range in four out of five races (a special Congressional election in California last November, the governorships of New Jersey and Virginia, and the recent special Senate election in Massachusetts) held since the Democratic controlled House of Representatives narrowly passed “cap and trade” legislation last June.

To what extent to we think that this “Obama plunge” will fuel major Republican gains in the House of Representatives this fall ? We will analyze what we think will happen based on actual data. In other words, the 2008 Presidential and Congressional vote will first be considered, then we will factor in the Congressional voting records on the following three pieces of controversial legislation that had almost unanimous GOP opposition: (1) the stimulus bill, which passed a year ago on a 244-188 vote, (2) “cap and trade” legislation which passed 219-212 last June, (3) the House version of the healthcare bill which passed 220-215 last November. Furthermore, this analysis will focus only on those 210 (out of 435) House districts where Obama carried a Republican held district, or where a Democrat holds a seat where Obama got 65% of the vote or less. It is also worth noting that as this article is being written, filing deadlines have only passed in four states (Illinois, Texas, West Virginia, and Kentucky), so there is a lot which could still happen between now and November.

Part 1: 2008 Presidential Vote

If one were to assume that the “Obama plunge” means that any retiring or incumbent Democrat in a district that voted 65% or less for Obama would switch parties, that would suggest a GOP gain of 165 seats (166 seats that flip to the GOP, while factoring in the loss of Joseph Cao’s seat in New Orleans, which voted 75% for Obama). In other words, a House of Representatives that in January 2011 would have 343 Republicans and 92 Democrats. However, this scenario is extremely unlikely, because (1) it assumes a uniform “Obama plunge” of 15% in each Congressional district, (2) it ignores the fact that the November election consists of 435 individual House races that may or may not have strong GOP (or Democratic) candidates, (3) the possibility of third party candidacies’ siphoning off votes from either party and altering the outcome of several races, (4) this analysis assumes that the GOP will win all open seats, and (5) with the election nine months away, we don’t know what voter attitudes will be when they go to the polls this fall.

Part 2: 2008 Congressional Vote

Because Presidential voting is not the best predictor of who will win 435 individual House races, we will add in another variable to those 210 House races we’re analyzing to refine our predictions – the incumbency factor. As in, if an incumbent Democrat received more than 65% of the vote in his/her 2008 race, he/she is theoretically safe from any “Obama plunge.” Applying this second variable suggests a GOP gain of 90 seats (91 seats gained, plus the loss of Joseph Cao’s seat in New Orleans). While a 90 seat gain would give the GOP 268 seats (and comfortable control of the House), there is another crucial factor that has been left out: the voting record of incumbent Democrats on the stimulus, “cap and trade”, and the House version of the healthcare bill.

Part 3: Voting record on major legislation in 2009

Even “throw out the bums” elections aren’t always predictable, because an incumbent’s voting record may/may not save a Congressman/woman from voter wrath. However, we can further refine our predictions by adding a third variable: how an incumbent Democrat voted on the stimulus, “cap and trade”, or the House version of healthcare. If we were to assume that an incumbent Democrat who voted “no” on two (15 more Democrats would fall into this category) or all three bills (two more Democrats would fall into this category), we would be looking at a GOP gain of 73 seats (74 seats gained, plus the loss of Joseph Cao’s seat in New Orleans), which would give the GOP 251 seats in the House. Curiously, 47 of the 74 theoretically vulnerable Congressmen/women were elected in the Democratic “wave” elections of 2006 or 2008, which suggests that their fortunes are tied to that of the Obama administration, for good or for ill.

Having laid out these three very to mildly optimistic scenarios for the GOP, there are still other variables which can’t be accurately predicted this far in advance of the balloting, such as:

• The fact that filing hasn’t closed in 46 states;
• Which incumbents of either party may choose to retire – while an article in POLITICO offered some clues, these things aren’t always predictable;
• Not all open seats that are GOP or Democrat held will be captured by the GOP; even in GOP landslide years of 1980 or 1994, Democrats still picked up a handful of GOP seats;
• Incumbents of either party can become ensnared in scandal between now and election day and lose, despite their or their districts voting record.

 As time goes on and we find out more about the 2010 landscape (for instance, the Illinois primary is on February 2, while later this month, candidate filing closes in Indiana, New Mexico, North Carolina, and Ohio), we will continuously refine our predictions. For now, one thing is certain: Republicans will only be a numerical majority if there is a net loss of 40 or more Democratic held seats.