Correction, 2:12 p.m. | There probably isn't a better demonstration of the nation’s partisan political polarization than the makeup of the Senate. Only 17 states have split delegations, while 33 states have either two Republicans or two Democrats (or two senators who caucus with the same party, in the case of independents).
Compare those numbers to the Senate makeup three decades ago, and the change is clear. After the 1982 elections, 24 states had split delegations, while 26 had two members of the same party.
Some of the changes show how state (and national) politics have evolved.
Thirty years ago, Kentucky had two Democratic senators, Walter Huddleston and Wendell Ford. But in 1984, Ronald Reagan carried the state by almost 20 points, running so strongly that he helped drag in an obscure GOP Senate nominee. That upset winner, Mitch McConnell, narrowly defeated Huddleston to begin the state’s transformation into a Republican stronghold in federal races.
In 1983, Democrats also held both Senate seats in Nebraska. Sens. Ed Zorinsky and Jim Exon weren’t your typical Democrats, which is why voters in a Republican state like Nebraska were willing to elect them. But that’s the point: It is almost unimaginable that Nebraska would send two Democrats to the Senate today.
Back then, Republicans held both Senate seats in Oregon, Minnesota and Virginia. Now, all six of those Senate seats are held by Democrats, though Virginia is a swing state and Oregon has become reliably Democratic in federal contests.
Vermont’s two Senate seats were split, with Republican Robert Stafford holding one and Democrat Patrick J. Leahy the other. It’s hard to imagine Republicans winning any federal election now in the Green Mountain State. Of course, Reagan got almost 58 percent of the vote in Vermont in 1984, while John McCain drew just over 30 percent in the state in 2008.
The change is particularly dramatic in the South, which has completed a regional realignment over the past 30 years.
By the early 1980s, many of the 11 states of the Confederacy had started electing Republicans to the Senate. After the 1982 elections, most Southern Senate seats were split between the parties. The exceptions were Arkansas and Louisiana, with two Democrats each, and North Carolina and Virginia, with two Republicans each.
Now, the only Southern states with split Senate delegations are Arkansas, Louisiana and North Carolina. Each of those states has a Democratic senator up for re-election, and in the current partisan environment, that’s an obvious problem for those incumbents.
Virginia, one of the first Southern states to vote Republican statewide, has become one of the first Southern states to slide back into the competitive column.
Of course, there are caveats and exceptions to every trend.
Senate nominees from the “wrong” party (that is, the minority party) still can win — as Joe Donnelly, D-Ind., and Claire McCaskill, D-Mo., did in 2012 — if the candidate who “should win” implodes.
There are also rare cases when the minority party’s Senate nominee is so strong and so politically independent that he or she can win (as Republican Mike Castle would have done in Delaware in 2010), or when a strong national partisan “wave” carries the minority party’s nominee to victory (e.g., Republican Mark S. Kirk in Illinois in 2010).
And there are still a few cases where an established senator has built up such good will that he or she can win in spite of his or her party (such as Maine Republican Susan Collins and West Virginia Democrat Joe Manchin III.)
But in general these days, states with a clear partisan bent are likely to favor candidates from one party or the other, making it more difficult for the minority party to win a Senate seat.
That development is a huge burden next year for both Arkansas Democrat Mark Pryor and Louisiana Democrat Mary L. Landrieu, both of whom need to persuade voters in their states not to do what voters almost everywhere else have been doing recently — see Senate elections more in partisan than in personal terms.
It’s also a problem for Democrats in West Virginia, where the party held both Senate seats in 1983 and, 30 years later, still hold both Senate seats. But the Mountaineer State is changing, and partisan trends clearly favor the GOP nominee next year.
Correction, 2:12 p.m.An earlier version of this post incorrectly referred to the number of states in the Confederacy.