Senator Chuck Hagel (R-NE) is retiring at the end of his term, and it's a loss for both Democrats and Republicans.
Former Nebraska senator and governor Bob Kerrey, a Democrat, is considering emerging from retirement to run for Hagel's seat, and the odds he would get it are high. Add in the fact that John Warner, a Republican, is vacating a Virginia senate seat that will likely be won by Mark Warner, a Democrat, and you've got what looks like a much small minority for the GOP.
By the way, there was once tons and tons of buzz around a Hagel candidacy for president. I was a somewhat-tongue-in-cheek proponent. I never really wanted the man to be president, but he was principled, reasoned, rational, and sincere. He'll be missed.
Update: Ed.-in-Chief Clara Jeffery writes in and speculates that Hagel's retirement clears the way for him to be Hillary's Secretary of Defense.