On November 2, 2010, Brewster won a special election to fill the remaining term of Senator Sean F. Logan, who had resigned his seat on August 24, 2010, to take a position at the University of Pittsburgh Medical Center. Brewster was sworn into the Pennsylvania Senate on November 17, 2010.
In July 2020, Brewster organized a meeting with bar and restaurant owners and signed a letter to Governor Tom Wolf urging him to lessen the restrictions on them imposed during the COVID-19 pandemic.[4]
He announced that he would not seek re-election to his seat in 2024.[5]
In January 2021, although Brewster narrowly defeated his opponent, Republican Nicole Ziccarelli, by 69 votes, the Republican-led State Senate refused to swear in Brewster for his fourth term, despite the fact that his win had already been certified by state officials.[6][7] Lieutenant Governor John Fetterman attempted to swear Brewster in. In a bizarre move, Republican leaders voted to remove Fetterman from his presiding role and halt Brewster's seating. Senator Jake Corman, when reading out names of the new and re-elected senators, intentionally omitted Brewster's, with Republicans once again voting to confirm the disruptive action.[8]
After a federal court ruling re-affirmed his win over Ziccarelli, Brewster was sworn in on January 13, 2021.[9]
