A head to head comparison of the Florida 2012 General Election gives us an idea of the break down of the voters.    

Barack Obama received 4,235,270 (50%) votes, beating Mitt Romney who gained 4,162,080 (50%) by 73,190 votes in Florida.

Mitt Romney won 54 counties whereas Barack Obama won 13 counties in the total of the 67 counties in the State of Florida.

Presidential General Elections

During the 2012 General elections, over 122M total number of votes were cast. Barack Obama got 62,614,654 (62.6 Million) over Mitt Romney's 59,141,654 (59.1 Million). He won the popular vote by 3,472,979 (3.4 Million). His victory at the State of Florida (with 4,235,270 votes) represents 6.3% of his popular vote victory. The remaining 49 states contributed to the remaining 93.7% popular votes victory.

Top 15 Counties in Primary Elections vs General Elections

All Candidates (General Elections)

These 15 counties play an important role in these Primary elections. If a candidate, can get a sizable majority in the larger counties (Miami-Dade, Broward, Palm Beach), it is still possible for other candidates to catch up, given the amount of large counties.

Top 15 Counties Comparison in Primary Elections vs General Elections

General Elections
Barack Obama

General Elections
Mitt Romney

Miami-Dade, Broward, Palm Beach, three of the larger counties, voted in favor of Obama giving him a 567k vote advantage. Lee, another larger county voted in favor of Romney giving him a 44k voter advantage in that county. However, Romney's steady win in the less dense counties wasn't enough to catch up, making Obama gain an upper hand in the State of Florida.

Related References: 2016 Florida Primary Election Story, 2016 Florida General Election Story 2020 Florida Primary Election Story