I truly don't understand why this is a controversial point to make. When a party is in some level of government and is unpopular, it can usually lead to voters disliking that party beyond just one specific area, especially in traditional swing states like Florida. I don't think that Obama can just come in a run against Scott directly, or anything, but having a deeply disliked and unpopular Governor certainly advantages Obama and the Democrats in general.
I realize this is slightly unrelated, but when I was watching the Canadian election, where were some of the weakest areas of NDP gains, or where did they underperform in comparison to other areas? Where they were in government and slightly unpopular, people were not as enthusiastic as other provinces in supporting federal NDP candidates. This sort of stuff is common sense and often translates into a bleeding effect on other levels of elections.
Why does Scott make some voters more likely to vote for a Republican candidate? I sure as hell don't know. As others have said you're probably down to the really uninformed voters or the hardest of the hardcore. But the central point of what Badger, or Holmes, or Px75 are arguing makes perfect sense. A deeply unpopular Republican governor would obviously not help Republican prospects in that state. Duh.
Of course other Republican politicians in the state are on the reverse side of the coin fairly popular. I.e. Rubio, many of the Republicans elected to the House in November etc.