In the wake of last night's House vote to sue the president, new data from Nate Silver at FiveThirtyEight suggests that Democrats are actually talking about the possibility of impeachment of President Obama more than Republicans. Eleven out of 14 mentions of impeachment on the congressional record this July come from Democratic members of Congress; and the left-leaning MSNBC mentions impeachment five times more often than the more conservative Fox News.
Meanwhile, Democrats have raised more than $2 million via emails talking up the threat of impeachment hearings. The emails — sent in the names of VP Joe Biden, Rep. Nancy Pelosi, and other high-ranking Democrats — frequently imply that impeachment proceedings could begin at any moment, featuring subject lines like "Impeachment (TODAY)."
Silver notes that in 2006, Republicans similarly tried to rally their base against the possibility of impeachment. At that time, Fox mentioned the topic almost twice as often as MSNBC. For more information on the history of calls for Obama's impeachment, check out this timeline, which tracks the topic's development since 2009.