WASHINGTON – With the 2010 election year barely under way, two senators and one governor — all Democrats — ditched plans to run for re-election in the latest signs of trouble for President Barack Obama's party.

Taken together, the decisions by Sens. Chris Dodd of Connecticut and Byron Dorgan of North Dakota as well as Colorado Gov. Bill Ritter caused another bout of heartburn for Democrats as they struggle to defend themselves in a sour political environment for incumbents, particularly the party in charge.

As 2009 ended, Democrats watched a string of their House members announce retirements and one congressman defect to the GOP.

Now, with Dodd, Dorgan and Ritter out, Republicans have even more to crow about, if not better opportunities to pick up Democratic-held seats.

Democrats, who have a 60-40 Senate majority that includes two independents who vote with them, now will have to defend four open seats in the Senate. The others are Delaware and Illinois, where Sens. Ted Kaufman and Roland Burris were appointed to the seats vacated by Vice President Joe Biden and Obama. Kaufman and Burris are not running for election to the seats.