A liberal-blogger cause du jour is to smack down talk that Democratic oversight hearings risk a backlash-inducing overreach. I don't think we're close to that point yet myself. But it clearly is a potential danger--even Henry Waxman told me so shortly after the election. And although poll numbers like these do show public satisfaction with Democratic investigations thus far, the obvious point is that Democrats want to be ahead of such polls, not following them. You can't wait until voters think you've gone too far to dial it back; by then the damage has been done. (Go ask ex-senator Al "Whitewater Show" D'Amato.)
Some of this is just tonal. I'm pretty sympathetic to the oversight hearings I've seen thus far. But I've also seen some gratingly self-righteous grandstanding (usually by back-bench members reveling in the spotlight) which, to the extent the average citizen notices, can't be helping the party.
It's also worth noting that, despite support for oversight specifically, the overall approval numbers of Congressional Democrats have declined since the election. One friend on the Hill argues that's a reflection of general disgust with Congress and Washington than any opinion on Harry Reid and Nancy Pelosi specifically. It's still not good news for Democrats.