Democratic officials tell The Associated Press that Connecticut's Christopher Dodd plans to make an official announcement today.
North Dakota Democrat Byron Dorgan said yesterday that he won't seek re-election to the Senate in November.
Adding to the party's concerns was word that Colorado Gov. Bill Ritter, considered a rising star in the Democratic Party, won't run for a second term in November. Ritter is also expected to make an announcement today.
The decisions come amid rising anti-incumbent sentiment among the electorate. A majority of the country says it's on the wrong track, and the party in power typically gets blamed.