Gauging Momentum in House and Senate Races

Gauging Momentum in House and Senate Races

By Sean Trende - October 28, 2010

With just a few days before Election Day, it has become increasingly clear that the Republicans are poised to take control of the House of Representatives. At the same time, however, the Republicans' chances of taking the Senate look to have faded somewhat as Democrats appear to be extending leads in races in California, Connecticut, and West Virginia. The momentum seems to be different in each chamber.

Part of this is the inherently different nature of House races and Senate races. Senate campaigns are typically trench warfare between well-funded, experienced politicians, who blast away at each other for the better part of a year in an attempt to move the polls. Once the primary concludes and the initial battle lines are drawn, there doesn't tend to be much movement until the end. House races, by contrast, involve lesser-known politicians with fewer funds, and tend not to engage until much later in the cycle.

Along the same lines, we have much better access to information about Senate races. People start polling them in the springtime, allowing us to gauge where they stand. But House races are notoriously underpolled. Everyone suspected that Baron Hill in IN-09 was in some degree of trouble this cycle, but we didn't get our first independent poll of the district confirming this until a week before Election Day.

Republicans have been roughly tied or ahead in the generic ballot since December of last year, so the House has been fully in play for almost a year now. Yet without reliable polling in individual districts, we had little idea which exact seats were most likely to flip parties. In other words, some of what looks like momentum on the House side is just the lights coming on and revealing portions of a room that we always suspected were there, but just couldn't see.

But there's another important reason for the discrepancy. This years' Senate battle is being fought on highly favorable ground for Democrats, much more so than the House. First, let's look at the following table:

As you can tell by the left column, this table is sorted by PVI, which tells us roughly how Republican or Democratic a district is. The second column shows the number of seats held by Democrats in each category of PVI. There are 15 seats held by Democrats that are R+10 or more (i.e. if the national Presidential vote was split between the parties, we'd expect the Republican to carry the district by 20 points or more), nine seats held by Democrats that are R+7 to R+9, and so forth.

The third column tells us what percentage of Democratic seats in each category currently receive at least some type of rating by RealClearPolitics - in other words, all the Democratic districts that are not "safe." The final column gives the percentage of seats that RCP rates as Tossup, Leans Republican, or Likely Republican as of Wednesday afternoon.

As you can see, because of Democratic gains in Republican-leaning districts over the last two cycles, House Republicans have been waging this election on relatively favorable turf. If Republicans defeat every Democrat in an R+4 district or better, they'll pick up 47 seats. Almost 100 seats are held by Democrats in districts that were D+3 or better, i.e., in swing districts or districts leaning toward Republicans.

For Senate Republicans, however, it was a very different picture this year:

The first two columns list all Senate races and the state PVI's (cutoff at R+10) - Republican seats are red, Democratic seats are blue. The third column is the RCP Average as of about noon Wednesday in each state. States with asterisks don't have RCP Averages; I've just averaged the most recent polls there.

To take the ten seats they need to win the Senate, Republicans have to either run the table in every state that is D+5 or better, or make up for any misses in even bluer states. To put this in perspective, for House Republicans to pull off the same feat, they would have to pick up about 123 seats! The landscape is also more difficult for Republicans given that four of the GOP's five most Democratic seats are open this cycle.

Put in this context, Senate Republicans have actually fared about as well as the House Republicans, if not somewhat better. Republicans are favored to carry almost all of the even seats or better, and have put the D+1 to D+6 seats mostly into play. They've even managed to put some of the D+7 or better seats fully into play. All of this is consistent with a strong GOP wave this year.

In fact, Democrats have dodged a major bullet by having so many heavily blue seats on the ballot this cycle. The Republicans are largely running the table in EVEN states or better, and are keeping D+1 to D+5 states competitive. The only thing keeping the Democrats from being decimated in the Senate is how few seats they hold in competitive states.

But as this final table reveals, there are twice as many Democratic Senate seats in Republican leaning states in 2012 as in 2010 (eight); the same is true of 2014. There are seven Democrats in D+5 or worse states in 2012 and another seven in 2014. If the current GOP tsunami had hit in those years, it's likely we would see losses on a scale we've never before seen - around thirteen or fourteen Democratic Senate seats would probably be Tossups or worse. If the economy and public perceptions of the Obama Administration don't turn around in the next twenty-four months, it's possible that's where the Democrats could find themselves in 2012.

Sean Trende is senior elections analyst for RealClearPolitics. He is a co-author of the 2014 Almanac of American Politics and author of The Lost Majority. He can be reached at Follow him on Twitter @SeanTrende.

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