Brazilian prosecutors have filed corruption charges against President Dilma Rousseff's electoral strategist.
Joao Santana was widely seen as the architect of Ms. Rousseff's 2010 and 2014 election victories. He has denied receiving bribes in a scheme to divert funds from the state-run oil company Petrobras.
About 50 Brazilian politicians, including the leader of the lower house of Congress, are under investigation in the Petrobras corruption scandal.
Mr. Santana is accused of receiving bribes from several large engineering conglomerates. Analysts say his arrest is a further blow for President Rousseff who is facing impeachment proceedings.