Can you point to where you found the “Clinton 52% Trump 48%”?
Go to the below website that contains realtime voter statistics. Then click on "by Party", and make sure to select 'include mail in and early voting'.
Hillborough voting stats
I calculated the numbers by first assuming Trump is leading the unaffiliated by 3%, and just for simplicity all Dems are Hillary, and all Reps are Trump, I multiplied unaffiliated by '.515'. I then add that to the total number of Republican voters, and divided by the total number of votes cast. That should give you a number of around '.479'.
So, with basic conservative assumptions that Trump has 3% advantage in unaffiliated, and total parity in crossover votes, Trump should have 48% of the votes cast in Hillsborough county.
The comparison to 2012 comes from
2012 Florida results