I think that Bill Frist's mistake was assuming that more than a few Senate Democrats would actually act in good faith, and limit their opposition to nominees tainted by "extraordinary circumstances". What he fails to appreciate is that to most Senate Democrats, being a mainstream conservative is "extraordinary" in and of itself. And they don't mean that in a good way. To the Democrat leadership, even a mild-mannered, rational man such as Bill Frist is a dangerous radical who must be defeated at any cost. He opposes their concept of progress - and "Progress" is their deity.
Huge mistake. Which goes back to his lack of political experience.