After the party lost the governorship in 2016, the 2020 Partido Popular Democratico primary for governor saw three candidates trying to become the PPD nominee, Senate minority leader Eduardo Bhatia, San Juan mayor Carmen Yulin Cruz Soto, and Carlos "Charlie" Delgado Altieri.
While Bhatia led throughout most of the campaign period Charlie pulled ahead during July and August, being at 44% to Bhatia’s 26% & Carmen Yulín’s 16% in a Radio isla poll, and Charlie was at 39% to Bhatia’s 35% to Yulín’s 21% in a Radio Isla poll.
Overall Charlie’s win can be attributed to a few factors:
1) Bhatia’s support for the privatization of the Energy distribution system in Puerto Rico, and the resulting in the Unions campaigning hard against him
2) Carmen Yulín being seen as an Independentista by the electorate, in addition to her bad record as Alcaldesa(Bhatia & Charlie both were fine with ELA though Bhatia favors closer ties with the US)
& 3) Institutional Support for Charlie from most of the PPD Municipal establishment, while they had similar support among the legislative establishment (though Charlie Edged out Bhatia).
Regardless of the factors, Charlie was able to Landslide the competition to win the PPD Nomination, Performing Strongest in his native Northwest corner of the island Around Isabela, Charlie won all but 2 Municipios, Guaynabo and San Juan, both Bhatia's Yulíns home base.
However, Charlie performed poorly relative to his results in the Urban cores which were Bhatia’s & Carmen Yulín’s base of support, due to Charlie Delgado underperforming with, though still winning over some, social Liberals in the PPD primary, thanks to the union campaign against Bhatia and Charlie's establishment support
Furthermore, Charlie’s underperformance with Social Liberals in this primary due to his social conservatism would turn out to be a foreshadowing to the General Election where his Collapse with them in the San Juan Metro would end up costing him the governorship.
In summation, Due to having more institutional support, Bhatia supporting Privatization, and Yulín being incredibly unpopular with the PPD Base, then Isabela Mayor Carlos Delgado Altieri was able to win the PPD Nomination in a landslide.
Taking a look at the Results by Legislative district the coalitions become clearer, with Charlie winning 36/40 house districts & 7/8 Senate Districts, Bhatia winning 3/40 House Districts and one Senate District, and Carmen Yulín winning 1 house district and no senate districts.
Similar to the results by Municipio Charlie's worst areas were the inmediate Ponce Metro, Metro San Juan, Metro Caguas, and Guayama Salinas Corridor.
Lastly, I'll note that Mayagüez is similar to these municipios in political culture, but because of Charlie's Home region advantage he was able to pull strong margins in the longtime PPD Stronghold.