Peru's presidential candidate Veronika Mendoza speaks during a presidential debate in Lima, Peru, April 3, 2016. REUTERS/Mariana Bazo

(Reuters) - Leftist presidential candidate Veronika Mendoza edged up in a poll ahead of Sunday’s election in Peru but remains in a technical tie for second with Wall Street favorite Pedro Pablo Kuczynski, according to a survey from Datum seen by a source on Thursday.

Center-right Keiko Fujimori maintains a wide lead with 43 percent of valid votes, which excluded likely blank and spoiled ballots in a mock vote, but that would not be enough to avoid a run-off. The survey from April 4-6 has a 2.2 percent margin of error.