BRASILIA, Nov 21 (Reuters) - The Brazilian Social Democratic Party (PSDB) was unable on Sunday to nominate its presidential candidate for next year"s election because of a voting app failure, delaying a decision between the main contenders, Joao Doria and Eduardo Leite. The center-right party paused voting after the app failure denied access to many of the 44,700 members registered to vote, including former President Fernando Henrique Cardoso. The party said it would extend voting until next Sunday if the technical problem can be resolved, leaving in suspense the tight nomination battle betweentwo governors, Doria of Sao Paulo state, Brazil"s largest, and Leite, of Rio Grande do Sul. Leite is seen as a centrist who is closer to the roots of a party that has shifted right since it held office in Brasilia. The PSDB governed Brazil from 1995-2002 during Cardoso"s two terms that modernized the economy and started social welfare programs that were later continued by leftist governments. The party"s role in Brazilian politics has since diminished and it now holds just half the seats it had a decade ago in Brazil"s Congress. In the 2018 election, won by far-right President Jair Bolsonaro, the PSDB"s candidate, Geraldo Alckmin, won just 4.8% of the vote. The party hopes to field a candidate who can be a centrist alternative in 2022 to Bolsonaro and leftist former President Luiz Inacio Lula da Silva, who has a comfortable lead in early opinion polls, although he has yet to declare his candidacy.