A huge fraction of Americans believe that impeachment of Bush (remember - merely a process to weigh the evidence and indict or not) should have been serously pursued by the House. Only one strategy might have worked: send a clear message that unless the House held serious impeachment hearings, then people would NOT vote for ANY Democrats in 2008 but would sit out the election. That might have frightened enough House Dems.
And please explain why Obama, Clinton and McCain have not takes a public position favoring impeachment hearings (NOT impeachment, but HEARINGS!!!) which would not have caused a conflict with senatorial responsibilities? To the contrary, even senators should feel ashamed that the House has not lived up to its constitutional responsibility.
Without this meaningful threat all continued talk about impeachment is just mental masturbation.