As usual that depends upon how good a year the Republicans will have in 2010. If it is just a normal mid-term year in which the opposing party has the White House, the answer is there is no way to gain control of either house. In a year like 1994, there would be a decent chance of gaining control of the House.
There is no question about whether the Republicans will pick up seats in 2010 because they will. The only question is how many. Most analysts are predicting around a 20 - 25 seats pickup in the House. We have developed a formula for rating a House district by the probability of the Republicans taking a Democrat seat. These probabilities are based on what could be expected in a mid-term election where the Democrats have the Presidency. Using the races where the probability is over 50% would produce a gain of 32 seats. This still leaves the Republicans 9 seats short of regaining control of the house or 10 since it is highly doubtful that Representative Cao (LA-2) will get re-elected. Extrapolating from the gubernatorial elections in New Jersey and Virginia, there another 11 seats that are quite possible.
What makes us so optimistic? Let's take Virginia as an example since we have 2009 results from that state by congressional district. The worst probability is in district 9 which we have rated at a 29.4% chance of the Republicans winning this district. Surely an incumbent who did not even have Republican opposition in 2008, got a 35.59% margin against a Republican in 2006 and has been in office since 1982 has a safe Democrat district. However, McCain-Palin carried the district by 19%. In the race for governor, the Republican got 66.36% of the votes for a 32.81% margin. That leaves Congressman Boucher with a 2.78% margin to spare. Yet we gave this district only a very conservative 29.1% chance of going Republican. The second worst district in Virginia is district 11 which we gave a 44.1% chance of going Republican. Here Representative Connolly had an 11.72% margin but McCain-Palin lost by 15%. The Republican candidate for governor in 2009 got 55.25% of the votes for 10.66% margin which gives Rep. Connolly only a 1.06% margin to spare. This district went Republican from 1995 to 2008 so we have a one term incumbent but even here we give the Republican a less than even chance to win the district.
It would take a year like 1994 for the Republicans to produce still more Democratic seats going Republican. However, it looks like 2010 will be a repeat of 1994 at this point. There is a chance based on the Virginia results that the Republicans could do even better than they did in 1994 which would pick them up the 12 seats in the possible group for a total of 231 seats. The Republican high point for seats in the House is 232 seats. There are another 10 seats in the poor bet group including Virginia 11. That one plus Ohio 8 would match that historic high. All 10 of them would give the Republicans a 241 to 194 seat majority. If 2010 turns out to be a truly historic rejection of the left wing Democrat congress, there are another 16 more in the long shot group. Even with every last seat with any chance of going Republican would give the Republicans 1 seat less than the Democrats have now. The rest of the Democrat seats have a negative probability so we can forget about them.
For a table showing the House races in play ranked in order of probability of going Republican, see: 2010 House Target Districts. In the Senate things are much harder. See: 2010 Senate Races by State. The Republicans are handicapped in the U. S. Senate races because only 19 Democratic seats are up for grabs. Of these, in 3 of them the Democrats are a shoo-in (HI, NY (Schumer) and VT). Of the remaining 16 seats, 4 of them are definitely long shots (CA, MA, MD, and OR). Only 5 seats are likely to go Republican since they have a probability of over 50%.
Since the Republicans only have 40 seats, it is hard to see how they could pick up 11 or the 12 seats in play and that assumes they will not lose any of their current seats. They would have to pick up 6 of the 7 possible states. One can see picking up NV, WA and WI in a 1994 type year since Harry Reid appears to be in trouble but the last two of these are blue states. The bottom line is that an 8 seat pickup is the best guess with a chance at four more in Delaware, Illinois, Indiana and New York. It would take an overwhelming sweep to accomplish that and regain control of the Senate.
