The New York Times calls for Gonzales's impeachment. Chuck Schumer admits error on Alito, and calls for a special prosecutor to investigate AG Gonzales. Iraq is getting worse, and new strange allegations about Bush's spying program are emerging (and that's not including all the other criminal acts, Scooter Libby, reconstruction theft, etc). We're on a road that leads only to one place to the removal of an illegitimate and overreaching executive.
It's important to frame this by understanding that impeachment is always a political issue, and never a legal one. As such, the important question is not whether the President committed crimes, but whether there is a coalition behind restoring legitimacy to the political system. This coalition needs to have at its core a set of elite decision-makers who have decided that impeachment is the only option that will allow them to preserve something they value. In this case, Bush is threatening the very legitimacy of Congress, and House members and Senators worked hard to get where they are.
I know of several large advocacy organizations that could send emails to their base on impeachment, knowing that the response level would be high. But the tradeoff for them is to message around impeachment, or message around a policy objective that is more 'achievable'. Resources are not infinite. We're in fights on Iraq, Iran, executive privilege, student loans, SCHIP, CAFE standards, the farm bill, 12 spending bills, etc.