In mensalão, relator charges that vote-buying did take place

In the Brazilian Supreme Court trial of Penal Case 470, popularly
known as the big monthly allowance (“mensalão”), the relator, justice
Joaquim Barbosa, who lays out the evidence and analyzes the case file
for the other justices, has begun examining the charges against the
political core (“nucleo politico”). The charges in this part of the case
are active and passive corruption, money laundering and conspiracy
among political parties that were allied with the government during the
period 2003-2004.

According to Barbosa, although the defense denies it, there is ample
evidence that some R$55 million was transferred through the scheme set
up by adman Marcos Valério to the political parties PP, PL (now PR), PTB
and PMDB.

Barbosa’s oral presentation yesterday, September 17, lasted all
afternoon and discussed only the PP, which he pointed out was an
opposition party until it received over R$4 million and began voting
with the government.