LIMA, Peru — As the region’s leaders converged for a summit in this seaside capital, it had the feel of an escape from the scandals raging at home. But their meeting will be no respite.

In Brazil, the October presidential election was upended last week after its front-runner, former President Luiz Inácio Lula da Silva, surrendered to authorities to serve a 12-year jail sentence for corruption and money laundering.

President Juan Manuel Santos of Colombia arrested one of the chief negotiators of the country’s landmark peace deal with rebels, an ex-guerrilla named Seuxis Hernández. Mr. Hernández is accused of helping traffic 11 tons of cocaine.

Worse, the summit’s original host resigned the Peru presidency over corruption allegations. Pedro Pablo Kuczynski quit last month when opponents released leaked tapes in which members of Congress bragged about supporting the president in return for lucrative government deals.