https://www.predictit.org/Browse/Group/67/National
Prices are what one would pay to get a $1 per "share" payoff if you are correct. It is essentially a percent probability for the outcomes. These "shares" can be bought or sold on their open market at any time to any willing buyer. One could buy a "yes" or a "no" share on any of the outcomes and could then sell one or more shares later, at a profit or a loss depending upon how the process has moved in the meantime.
Democratic 67¢
Republican 36¢
Edited by JeffB at 11:36:00 on 07/29/16