President Barack Obama heads to California and Washington state this week to drum up support for endangered incumbents Barbara Boxer and Patty Murray in the last days of a campaign that finds his Democrats playing defense around the country.

Wins in those two Democratic-leaning states -- most polls show Boxer and Murray with slight leads -- likely would be enough to ensure Democrats retain narrow control of the Senate even if Republicans sweep the other competitive races.

"Right now, Democrats have their best chances on the West Coast. They are in relatively good shape out there compared with the rest of the country," said Steven Schier, a political scientist at Carleton College in Minnesota.

Public discontent with Obama and the economy has sparked widespread predictions of a Democratic election defeat, with Republicans favored to gain more than the 39 seats they need to seize control of the House of Representatives and perhaps even the 10 seats needed for a Senate majority.