AP notes that 54 Democrats entered the House in the sweeps of 2006 and 2008. Many come from swing districts or GOP-leaning constituencies. Now they have to defend tough votes on health and other issues.
Add to that the absence of Obama from the top of the ticket, which could reduce turnout among blacks, liberals and young people, and the likelihood of a highly motivated GOP base confused by the president's proposed health care plan and angry at what they consider reckless spending and high debt.
Taken together, it could be the most toxic environment for Democrats since 1994, when the party lost 34 House incumbents and 54 seats altogether. Democrats currently have a 256-178 edge in the House, with one vacancy. Republicans would have to pick up 40 seats to regain control.