If anything, the Democrats should be thanking him--he's lessening the temptation for the majority to start tearing every member of the administration to shreds and therefore making a showing as overconfident, greedy pricks in 2008.
Given that it didn't hurt the republicans in 2000 I don't see why that should be such an issue.
Not the same. The Republicans had held the majority for six years by the time 2000 had rolled around, so I'd say the American public had been quite happy with them by that time. The Democrats in 2006, on the other hand, were only elected because the public is telling the Republicans that they've gone too far and need to straighten up. The American people aren't embracing liberalism or the Democrats; it's simply a case of the lesser of two evils, and if the Democrats do anything to tarnish their image in Congress and the Republicans center themselves, they're in for a huge problem in 2008.