Julio Guzman said on Thursday he was rallying international support for his bid to be reinstated as a candidate for Peru's presidency after the electoral board barred him on a technicality one month before the election.
Guzman, 45, told Reuters in an interview he had started talks with four foreign governments - from Latin America and "other continents" - about the board's move, which prompted concern from a US lawmaker and the Organization of American States (OAS).
"My candidacy has been rejected in part because I'm the new kid on the block," Guzman said.
The electoral board's 3-2 decision to bar Guzman from the April 10 election because his party did not follow electoral procedures is expected to bolster centre-right front-runner Keiko Fujimori's chances of winning.
The board also disqualified another candidate for giving cash to poor voters while campaigning.
Guzman, a centrist economist, was running head to head with Fujimori in an expected run-off, according to opinion polls.
Fujimori and former President Alan Garcia, who is seeking a third term, have denied Guzman's allegations they pressured the electoral board to block him. Fujimori is the daughter of imprisoned former President Alberto Fujimori.
The board has denied acting on behalf of political interests, and no evidence of wrongdoing has emerged.
But the back-and-forth decisions on Guzman's candidacy, which started after his surprise surge to second place in polls, and the confusion over what he did wrong, has raised questions over the fairness of the election.
"This decision risks undermining the legitimacy of whomever should eventually prevail," US House of Representatives Foreign Affairs Committee Chairman Ed Royce said.
Guzman said he was also reaching out to the Inter-American Human Rights Commission, where he might file a lawsuit. The OAS will review the dispute as part of an electoral mission on Monday, he added.
In a statement, the OAS said disqualifications so close to elections created "uncertainty in both the electorate and the candidates."
Lawyers said Guzman had little chance of convincing the electoral board to reverse its decision in a last appeal, and that requests for courts to intervene could take months.
But Guzman expressed optimism the board might backtrack, pointing to electoral rules he alleged other parties also broke - raising the specter of six candidates being tossed from the race.
"If they let them take part and not us, then the elected authorities, from my point of view, would lack legitimacy," he said.