Here's a problem which will affect the winner. No economic expansion in American history has lasted more then 10 years which means the current expansion which end between 2017-2020 which could cause the party in power to all the blame.
For Democrats they most likely take back the Senate with a tie breaker with the Vice President but in 2018 they get slaughtered in the Senate and House like 2010 and 2014 and then with an economic recession, and likely high deficits, and foreign policy troubles in their term they will most certainly get all the blame as it is their third term and they don't have the ability to Blame Bush just like Bush Senior couldn't blame Carter for his woes and most likely be swept out of office in a realigning election just like 1992 was for the Democrats and lose the advantage they had in the Electoral College and the republicans would have filibuster proof majorities in Congress.
For Republicans it depends when the recession hits. If it hits early in his presidency they will be able to deflect some of the blame on Obama. But their advantage in 2018 congress will Disappear as despite a favorable map they wont gain any seats. If it hits late in their term they will be swept out of Office in 2020 just like Carter was in 1980 and The democrats will go from having an advantage in the Electoral College to a lock just like what happened in 1980 to the republicans
This is what Ive argued.
