They only had a true trifecta for a few weeks. You need 60 votes in the Senate to prevent a filibuster, and due to a lawsuit Al Franken wasn't able to take his seat until Ted Kennedy had stopped attending due to poor health, and when Kennedy died his appointed replacement wasn't able to take office until like November 2009, and the Tea Party won the special electuon to replace Kennedy and the Dems lost the 60-vote majority in January 2010.