Sen. Byron Dorgan (D-ND) "dropped a late-day bombshell, announcing he will retire when his term ends this year," USA Today reports.
"Dorgan's announcement represents an opportunity for Republicans: North Dakota is a Republican-leaning state, where President Obama got just 45% of the vote last year."
Most analysts now expect Gov. John Hoeven (R) to run. If so, he will instantly become the favorite to win this seat.