This is a big concern for the Democratic party heading into the 2010 midterm Congressional elections--and all the more reason why Obama is so frantically trying to pass sweeping health care reform now, rather than trying to do so later with probably a more meager majority.
Glenn Beck, Rush Limbaugh, Sarah Palin and others have the GOP base all wild eyed and frantic to get to the polls next year, whereas we can expect the Democrats to be comparatively lethargic after spending a ton of energy getting Obama elected last year....
Remember in 1994, two short years after Bill Clinton came into office after trouncing George Bush Sr. the Dems were pummeled into submission by the Newt Gingrich led Republican revolution.
The country has changed quite a bit in the 15 years since then (mostly in terms of demographics--tons more Hispanics, etc.) and the likelihood of the GOP matching their '94 result is almost nil. But as this poll shows us, the probability is that the GOP makes gains.
If you are a Democrat, take a good long look at the picture in the upper right. And vote next year for goodness sake--