Arabela Carreras became Río Negro's first female governor-elect on Sunday after securing 52.44 percent of the vote against rival candidates.
The win is another case of "the lesser of two evils" for the Mauricio Macri administration, with Carreras keeping the Kirchnerite candidate Martín Soria, with 35.04 percent, out of office.
A similar situation played out last month in Neuquén province with a sitting-government candidate, Omar Gutiérrez, re-elected against Macri and Kirchner-aligned contenders.
In Río Negro, Macri's candidate, Lorena Matzen, drew a meagre 5.67 percent.
Matzen's UCR Radical Party is a coalition ally of Macri's.
Tensions are brewing in the Cambiemos (Let's Change) coalition over the preferencing of candidates from Macri's PRO Party for top government and legislative tickets.
"I lament very much that there are celebrations in Government House because here we've been flying the flags of the national government", Matzens told the A24 news channel.
She said she was "especially" upset about the sentiment reportedly manifested by "some leaders who expressed their support for the politicla movement which is governing today", in reference to the sitting provincial government of Governor Alberto Weretilneck.
Carreras is the province's outgoing Tourism minister. She took the top spot on the provincial government's ticket after Weretilneck was banned by court order from running for re-election.
Over half a million Rio Negro residents voted on Sunday, or 73 percent of eligible voters, the province's Electoral Commission reported.
Carreras, who represented the "Together We're Río Negro" alliance, celebrated her victory in her home city Bariloche on Sunday, where she promised "continuity".
"This dream began and was continued by Alberto Weretilneck", she said.