Can an Incumbent Senator Lose Re-election?

Sen. Mark Udall

One of the commenters to this blog pointed out the last time an incumbent U.S. Senator lost re-election in Colorado was in 1978. Indeed, Republican Bill Armstrong defeated one-term Senator Floyd Haskell, who switched parties in the early 1970s over the war in Vietnam. Republicans were especially angered by Haskell’s switch, and Armstrong represented the rising new Reagan Republicans.

But, there are times when the political environment becomes unstable and incumbents vulnerable. In fact, three incumbent Colorado senators lost their re-elections from 1972 to 1978. Gary Hart defeated incumbent Republican Senator Peter Dominick in 1974 at the height of the political crisis caused by Watergate and the Vietnam War. And Haskell, himself, defeated an incumbent senator, Gordon Allott, in 1972 mostly due to the Vietnam War and the anti-Olympics vote (61% support).

In other words, there are moments, such as the 1970s, when the political environment becomes volatile and voters become especially incensed, causing incumbents to lose. Is 2014 one of those years?

The table below shows the recent history of Senator Udall’s seat, which has two incumbents losing.