Although the PTN never became as influential as the three main parties of the Fourth Republic (the PTB, PSD and UDN), it did serve, from 1954 until its dissolution in 1965, as the political vehicle for one consequential figure, Jânio Quadros, governor of São Paulo (1955–59), and very briefly president of Brazil (January 31 to August 25, 1961).

Quadros' premature resignation from the presidency, in a failed gamble to increase his powers, triggered the Legality Campaign (a Campanha da Legalidade), which contributed significantly to the political instability leading to the military coup of 1964.

The PTN was formed in 1945 by people linked to the Ministry of Labour who were seeking to create a trade union movement independent of Getúlio Vargas's PTB.

The PTN put forward its own candidate, Hugo Borghi, for the governnorship of São Paulo, but he was defeated by Lucas Nogueira Garcez of the PSP.

In São Paulo, the PTN elected five federal deputies (Emílio Carlos, Dario de Barros, Joaquim Coutinho Cavalcanti, Nélson Omegna, Alberto Botino), and just one in Goiás (João d’Abreu), in coalition with the PSP.

Ahead of the 1955 presidential elections, the PTN's national convention confirmed its support for the candidacy of Juscelino Kubitschek, launched by the coalition of the Social Democratic Party (PSD) and the PTB.

A few days later, the PTN voted in favour of the impeachment of former President João Café Filho, preventing his return to power.

In the 1958 elections, the PTN maintained significant growth in São Paulo, electing, in coalition with the Christian Democratic Party (PDC), Carlos Alberto de Carvalho Pinto to the position of state governor, and eight deputies to the Federal Chamber (Emilio Carlos, Olavo de Castro Fontoura, Rui Novais, Gualberto Moreira, Harry Normanton, Hamilton Prado, Luís Francisco da Silva Carvalho and Miguel Leuzzi).

Emílio Carlos and Jânio fought for the nomination of Fernando Ferrari (then a member of the PDC, and formerly of the PTB) as vice-presidential candidate.

This led to division in the electorate and resulted in the reelection of PTB candidate João Goulart, this time the running mate of Henrique Teixeira Lott.

Once Jânio was elected and his mandate had started in January 1961, he steered an erratic course both in domestic and foreign policy, which alienated him from supporters on both his left and his right.