A demonstrator shout slogans during an anti-government protest in Sao Paulo, Brazil, April 12, 2015. [Photo/IC]

Still, many analysts predict that lower turnout Sunday protests could spell the end of the movement.

"I do not think we will see the protest movement grow in size and frequency," said Carlos Lopes, a political risk analyst at Brasilia office of the Insituto Analise consultancy. Given Sunday's smaller turnout, "people will be less inclined take part in future demonstrations and the movement toward large-scale rallies will begin to fizzle out."

One of the heads of the Movimento Brasil Livre, or Free Brazil Movement, which helped organize Sunday's demonstrations rebuffed the suggestion that turnout was down, stressing that many more cities and towns staged protests than last month.

A survey released Saturday by the Folha de S.Paulo daily found that 63 percent of Brazilians surveyed supported impeachment proceedings against Rousseff, while 33 percent opposed them. The same poll, by Datafolha, showed Rousseff's approval ratings holding steady, with 13 percent of respondents giving her a great or good rating while 60 percent of respondents evaluated her performance as bad or terrible. The survey of 2,834 people in 171 municipalities was conducted on Thursday and Friday. It had an error margin of plus or minus 2 percentage points.

Much of the protesters' ire focused on the Petrobras scandal. Prosecutors say at least $800 million was paid in bribes and other funds by construction and engineering firms in exchange for inflated Petrobras contracts. Rousseff, a former chairwoman of Petrobras' board, has not been implicated and so far is not being investigated, though two of her former chiefs of staff are among the dozens of officials caught up in the inquiry.

One president, Fernando Collor de Mello, has been impeached since Brazil's return to democracy in 1985, but many legal experts have said that Rousseff could only be impeached if evidence emerges directly linking her to crimes committed during her second term, which began in January.