My forecast for the 2014 state legislative elections indicate that the Democrats will lose majorities in five state Senates and nine state Houses. Those state Senates are Colorado, Iowa, Maine, New York and Washington, while the state Houses are Colorado, Kentucky, Maine, Minnesota, Nevada, New Hampshire, New Mexico, Washington and West Virginia.

Forecasts were generated from analyses of the 77,844 contested state legislative elections that occurred between 1968 and 2012. National conditions such as the state of the economy, presidential approval, midterm penalty, Congressional vote intention  have a large effect on state legislative elections and work against the Democrats this year. The forecast also took account of factors specific to individual races, such as incumbency and prior vote in the district. This table has all forecasts at the state legislative chamber level.

Forty-five states will have elections to their state legislatures this coming Tuesday, although four of those states do not have elections to their state Senates (not including special elections). Democrats are likely to lose seats in most states. The only gains are forecast to come in the Oregon, North Dakota, and Rhode Island State Senates, as well as the North Dakota House. West Virginia is forecast to see especially large losses for the Democrats in both of its chambers. Other states will see losses for the Democrats of over 10 percent, including the California Senate, the Nevada House, and both chambers of the Maine legislature.

Of the five state Senates that Democrats are forecast to lose, the New York state Senate is the most competitive overall, with a 46 percent chance of Democratic control. In the Washington state Senate, Democrats have a 25 percent chance, with the other three having even lower percentages. Among state Houses that the Democrats are forecast to lose, Nevada is the most competitive (46 percent chance of retaining control), New Mexico is the second most (31 percent), and the others are at 25 percent or less.

The Republican wave could, of course, extend more widely, but taking many more chambers than those already listed is not likely. The Oregon state House has a 54 percent chance of going to the Democrats, so it is a very plausible target for the Republicans, but Democratic majorities in state Houses are virtually assured after that. Republicans may also pick off the Connecticut state Senate (67 percent chance of Democratic control) or the Nevada state Senate (79 percent chance of Democratic control) but these are long shots and no other possible targets show themselves after those.

The upcoming election sees 26 partisan state senates with half (or in one case, one-third) of their seats up. That means that holdover state senators — those elected to four year terms two years ago — will play a major role in which party controls those state senates. The surprising seat gains predicted for Democrats in North Dakota is explained by holdover legislators. First, it should be noted that even if the forecast is correct, the Democrats will still be left with a mere 34 percent in the senate, and 26 percent in the House. In the state senate, 10 out of 23 of the holdover state senators are Democrats. That is still a minority, but it brings their average up. Next, the North Dakota House of Representatives is the only lower chamber in the country that has holdover lawmakers because of its staggered four-year terms. Again, the Democrats have a non-trivial minority of holdover state House members (14 out of 46) which is not much, but like in the state Senate, it offsets the losses they are predicted to have in the races that are up.

Why does this forecast suggest Democratic losses? A key reason is that national conditions do not look good for the Democrats. Congressional vote intention and presidential approval imply a large wave in favor of the Republicans, although the state of the national economy is not as bad as one might expect.

To capture congressional vote intentions, I averaged two polls — one by Fox News (Oct. 12-14) and another by ABC News / Washington Post (Oct. 9-12). An average of 50.6 percent of registered voters in these polls said they would vote for Democrats in the upcoming U.S. House election (of those saying they would either vote for a Democrat or a Republican). Because historical statistics for congressional vote intention are for national samples of citizens not registered or likely voters, I convert that 50.6 percent figure above to an estimate for a national sample, which would be 51.5 percent. Comparing to surveys asked at around the same time, this is very close to other historic lows for the Democrats in the 1968 to 2014 period: in 2010, 49.3 percent said they would vote for a Democrat for Congress, while in 1994 49.5 percent did. (Generally, a good rule of thumb to use with Congressional vote intention is to subtract 5 percent for the percent of voters who will vote for Democrats on Election Day.)

The presidential approval rate of 40.6 percent that Obama received on Gallup polls taken Oct. 13-19 also implies trouble for the Democrats. Between 1968 and 2014, this approval rate is ninth from worst, while it is 39th from the best. For midterms from 1968-2014, only 1986 and 2002 saw presidential approval ratings boding this much ill for the Democrats (and in both cases the Republican president’s popularity was offset by the midterm election penalty). Obama’s current approval rating is almost exactly what Clinton’s was immediately before the 1994 elections (41.0 percent).

The national economy — represented here by a weighted average of real quarterly income growth, is actually not as bad as one might expect. Growth was 2.4 percent, which for the 12 midterm election years examined here (i.e., even non-presidential years), is only beat by four other elections.

The above factors suggest that voters punish the party of the president in state legislative elections in midterm years. For this reason, Democratic state legislative candidates can expect to lose three quarters of 1 percent compared to two years ago, if that is the last election they ran in.

Taken together, these factors explain why the Democrats are predicted to lose state legislative seats all across the country.

Carl Klarner is a visiting scholar at Harvard University.