Born together as part of the social democratic opposition to the military dictatorship from the late 1970s through the 1980s, and later shifting toward neoliberalism and liberal conservatism in the 1990s, the PSDB and the PT have since the mid-1990s been the bitterest of rivals in current Brazilian politics—both parties prohibit any kind of coalition or official cooperation with each other at any government levels.

Famous tucanos include Mário Covas, Geraldo Alckmin, Tasso Jereissati, Aécio Neves, former President Fernando Henrique Cardoso, Franco Montoro, Aloysio Nunes, Yeda Crusius, João Doria, and José Serra.

With the imminent collapse of the military dictatorship in the early 1980s, a group of left-wing intellectuals were mobilized to create a leftist party.

Some of them attempted to work with the labour movement led by Luiz Inácio Lula da Silva, but the group split over ideological grounds.

On 21 April 1985, President-elect Tancredo Neves died, having been the last President not elected directly by the people since the beginning of the military dictatorship.

A high proportion of the first members of the PSDB came from the so-called "historic PMDB", which was and still is a very large party with many internal conflicts.

Some of the founding members were José Serra, Mário Covas, Ciro Gomes, André Franco Montoro, Fernando Henrique Cardoso, Aécio Neves and Geraldo Alckmin.

[28] The 2011 book A Privataria Tucana, written by journalist Amaury Ribeiro Jr., a former special reporter of weekly magazine ISTO É and daily newspaper O Globo, highlighted documents that show alleged irregularities in privatizations that occurred during the administration of the former President Fernando Henrique Cardoso.

[29] Although the PSDB declares itself as a centrist party, some people on the left reject this definition, especially after Fernando Henrique Cardoso embraced Third Way politics as president.

[...] A rhetoric of overcoming classical ideological division [...] was one of the justifications of the grand parliamentary alliance with center and right-wing parties.

[46] Political scientist Glauco Peres notes that the party's move toward conservatism came "in stages," from "the liberal policies and major privatizations of the Cardoso era" to the gradual emergence of a "conservative and religious discourse" in the early 2010s to the failed campaign of the party's right-wing presidential candidate Aecio Neves in 2014.

[...] A social democrat is before anything else someone who has critical sense — who realizes the injustices of society and has no fear to oppose them, even at the risk of being taken as a subversive or a dreamer".

Many leaders of the party come from these regions, like Tasso Jereisatti, Aécio Neves, Teotonio Vilela Filho, Cassio Cunha Lima, Sergio Guerra and Simão Jatene.

Dória is often accused of populism, demagoguery, opportunism, personalism, self-promotion, market fundamentalism and aggressive exploitation of anti-Workers' Party sentiment within the populace.

The key reasons for this failure were the corruption scandals of Aécio Neves, the party's support for the government of Michel Temer, the lack of charisma and wrong strategies of Alckmin in the presidential campaign, which chose to attack the right-wing populist candidate Jair Bolsonaro from a progressive viewpoint instead of attacking the traditional rival PT, and a continuing domination of old leftist leaders instead of new and more liberal members with stronger connection with the voter base over the party.

The PSDB faced a runoff in three of the four biggest states, namely São Paulo, Minas Gerais and Rio Grande do Sul, all of them with more pro-free market and centre-right views than Alckmin.