The Oklahoma Democratic Party had their 2007 state convention last week and passed a bunch of resolutions. The resolutions look a lot like a platform the way they are presented on their blog, but they call them resolutions instead of a platform. Maybe, unlike the TDP, they don't have separate platform and resolutions committees in Oklahoma. At any rate, one of the approved resolutions says,
"IMPEACHMENT OF PRESIDENT GEORGE W. BUSH AND VICE PRESIDENT DICK CHENEY
We support an investigation by the United States House of Representatives that will in our opinion lead to the impeachment of President George W. Bush and Vice President Dick Cheney.
This news article from NewsOK.com mentions the impeachment resolution. I am guessing that they first had a stronger statement and it got watered down to the one that passed.
At the 2006 TDP State Convention more than 30 percent of the delegates signed an impeach Bush resolution, but it failed on the floor of the convention. Watch the video of that floor debate.