I believe there are two elements that have to be in place to impeach a public official. First, there has to be some legal infraction. This is minor. If you can't find an infraction, you can always get the target to lie about something. That's what Newt Gingrich and Ken Starr did to Bill Clinton. What's more important, IMO, is to have public opinion driving the process.
So how can news about the drive to impeach Bush be elevated to the level of a celebrity trial?
I don't remember Andrew Johnson's impeachment, so I have only two examples to go by -- Nixon and Clinton. What were the ingredients that drove these impeachment proceedings?
Clinton's impeachment was simple. It was the sex life of a celebrity that drove the public's interest. Whether it's Monica's dress or Michael's underwear, people can't resist reading about semen stains. It's something they can identify with. Moreover, the reporting wasn't dry political intrigue. Drudge was (is) more like the National Enquirer than the Washington Post. I see Clinton's impeachment as political masturbation. If it weren't for Monica, they would have gotten him to lie about something else important, like his Twinkie consumption.
But republicans don't have sex (except for procreation and then, only in the missionary position), so Nixon's impeachment held some other attraction for the public. I believe it was the dime-store-crime-novel of the unfolding conspiracy. It was a real-world whodunit involving public figures. But even then, there wasn't a lot of public interest until the tape transcripts were released and middle America found out how one Quaker politico talked behind closed doors.
So why isn't the public demanding Bush's impeachment? They've heard him lie. There are pictures of him flipping the bird (and now, the Nazi salute). There are reports of him doing cocaine and urinating on cars. And there are countless examples of him actually doing impeachable offenses. So maybe the problem is that it's all too complicated for the public. We need somebody from the National Enquirer to distill all the intricacies of this crime novel into comic-book format.