Democrats have many more seats to defend (23-10), but several GOP moderates may be exposed to primary challenges. The 2010 election campaign is over, but 2012 is nearly upon us. Within weeks, we will know the candidates for president, and within months, preparations will begin for the 2012 Senate races. Which Senate seats are likely to be in play? Some of this will depend on how the next Congress shakes out, as well as what retirements occur, but several senators are already in danger.Republican in danger of general election loss: Senator Scott Brown (R-MA) shocked the political world by winning...