While the Republicans have 13 US Senate seats up for re-election in 2014, most of them are relatively safe. The Democrats have 20 seats up for re-election, including many in swing states and conservative states such as Louisiana, Arkansas, and South Dakota. All 20 Democrats will be facing voters for the first time since voting for Obamacare. How will they hold up to voters? The Democrats need to retain 15 of 20 seats to keep control of the chamber.