President Dilma Rousseff of Brazil is fighting for political survival as calls for her impeachment grow louder amid a widening corruption investigation and a tanking economy.

Astonishingly, however, she appears to have felt she had political capital to spare last week when she appointed her predecessor and political mentor, Luiz Inácio Lula da Silva, to be chief of staff, a move that largely shields him, for now, from prosecution in the corruption scandal involving his ties to giant construction companies.

Ms. Rousseff’s explanation was tone deaf and ridiculous. She characterized the appointment as an opportunity to bring back to the government a maverick politician and talented negotiator to help Brazil contend with an assortment of crises, including the spread of the Zika virus.

“If Lula’s arrival strengthens my government, and there are people who don’t want it strengthened, then what can I do?” Ms. Rousseff said.