The closest thing we have in order to measure the potential modern partisanship of Puerto Rico is the D/R presidential Primaries, Supper low turnout(however both were competitive in 2016), but it is the best estimate we have.
Here are are the numbers —————————————>
As we can see through the Primary estimates Puerto Rico would be a very Democratic State, will this hold up, who knows, however it is the best data out there so....
(Disclaimer Primary numbers are not the best representation of of who would win in a General election)
One method that can be used to calculate PR's Partisanship is using the stateside parties to determine the results of the Territory. Such a method(using splits from a Data for Progress Poll) showcases PR to be a 61.8% -37.5% Dem Leaning State.
In addition to that All Municipios are Dem leaning, with the least Dem leaning town with the splits seen above, being Dem by 6%, Said Municio.Florida in the north west coming in at (D)53.06% (R)46.25%
(one town got cut of from the spreadsheets Yauco at (D)61.65%to (R)37.75%)
I’ll say that through some debate and my knowledge of international parties, the PIP appears to be just a more economically left wing UK Labour Party. Problematic aspects included. Which is why it likely breaks down 75-25. D, considering that the candidate was a social Democrat.