As the race for the Brazilian presidency remains undecided after a first round of voting, BBC Latin America analyst Americo Martins looks at the other electoral contests which could play decisive roles in the run-offs.
The races for regional governments could prove key in the 29 October vote, and the two presidential challengers have wasted no time in trying to secure the backing of several influential gubernatorial candidates.
The two candidates are vying for the support of regional figures
President Luiz Inacio Lula da Silva, from the Workers' Party (PT), and his opponent Geraldo Alckmin, from the Brazilian Social Democratic Party (PSDB), are hoping the support of some of the better known regional candidates may win them votes.
Candidates in 10 of the country's 27 states - including Rio de Janeiro, the third most populous state - are facing run-offs.
Both presidential hopefuls are already holding talks with several regional candidates, including Sergio Cabral who is running for the Rio governorship.
They are also targeting people who voted for Heloisa Helena (PSOL) and Cristovam Buarque (PDT) in the first round of the presidential race.
GOVERNORS ELECTED SO FAR
PMDB (Party of the Brazilian Democratic Movement) - 4
PSDB - 4
PT - 4
Others - 3
Ms Helena, a former PT member turned critic of the government, has already declared that she will not back any of the candidates, saying she thinks they defend "the same liberal economic policies".
Mr Buarque, another ex-PT member and once a minister in Lula's government, is in talks with both Lula and Mr Alckmin. But he is giving signs that he will probably support the PSDB candidate.
Candidates from Lula's PT and Mr Alckmin's PSDB will face each other in only two states: Rio Grande do Sul, in the South, and Para, in the Amazon.
In the other states, the presidential candidates will try to make regional alliances with third parties.
Heloisa Helena has said she will not back either of the two
Lula is likely to concentrate his efforts in the southern parts of Brazil, where Mr Alckmin received strong support in the first round. The PSDB candidate, for his part, will have to work hard in the impoverished north-east, the president's stronghold.
Their parties won four governorships each in the 17 states where the regional races were decided in the first round.
While the PT won in some of Brazil's poorer states - such as Piaui, Acre and Sergipe - the PSDB had a strong showing in the two richest and most populous states: Sao Paulo and Minas Gerais.
Sunday's elections also produced significant changes in Congress.
After several allegations of corruption involving members of both houses of Congress, voters decided to elect several new faces - 46% of all deputies elected to the lower house are new to the institution.
Ex-President Fernando Collor, elected to the Senate, backs Lula
In the Senate, one of the big stories was the election of Fernando Collor de Mello to represent the north-eastern state of Alagoas. He will replace Heloisa Helena, who gave up her seat to run for president.
Mr Collor is the only president to have been impeached over corruption allegations in Brazil. After his impeachment, in the early 1990s, Mr Collor was barred from contesting elections for a period of time.
Now, he is back on the political arena, and he has already announced that he will support Lula in the second round.
"I believe that, among all the candidates, Lula is the one who is better prepared to face the needs and circumstances of Brazil - despite the police files," Mr Collor said on Monday, making a reference to the recent corruption allegations against PT.
COMPOSITION OF CONGRESS
Chamber of Deputies:
Pro-government - 322
Opposition - 191
Pro-government - 35
Opposition - 46
Whoever is elected president will have a very difficult relationship with Congress.
The parties that, on paper at least, back Lula elected 322 deputies.
If he is elected on 29 October this would, in theory, give him a comfortable majority in the 513-seat chamber. But the reality is that several of those lawmakers may vote against the government or try to make some sort of deal in exchange for their support.