Obama is relatively centrist. check.

....Think about 1994. Pundits credited major Republican victories to angry white men, Hillary’s failed healthcare plan, and Newt Gingrich’s “Contract with America.” But the defeat was equally rooted in a massive withdrawal of volunteer support among Democratic activists who felt politically betrayed. Nothing fostered this sense more than Bill Clinton’s going to the mat to push the North American Free Trade Agreement (NAFTA).

Angered by a sense that he was subordinating all other priorities to corporate profits, and by his cavalier attitude toward the hollowing out of America’s industrial base, labor, environmental and social-justice activists nationwide withdrew their energy from Democratic campaigns. This helped swing the election, much as the continued extension of these policies (particularly around dropping trade barriers with China) led just enough Democratic leaning voters in 2000 to help elect George Bush by staying home or voting for Ralph Nader.

No place saw a more dramatic political shift than my home state of Washington. In November 1992, Democratic activists volunteered by the thousands, hoping to end the Reagan-Bush era. On Election Day, I joined five other volunteers to help get out the vote in a swing district 20 miles south of Seattle. Volunteers had a similar presence in every major Democratic or competitive district in the state. The effort helped Clinton to carry the state and Democrats to capture eight out of nine House seats.

But by 1994 grass-roots Democratic campaigners mostly stayed home, disgruntled. In Washington State, there were barely enough people to distribute literature and make phone calls in Seattle’s most liberal neighborhoods, let alone in swing suburban districts. Republicans won seven of our nine congressional races, and reelected a Senator known for baiting environmentalists.

The same was true nationwide.

http://www.commondreams.org/archive/2007/11/27/5460/