* Socialist Castillo inches ahead in tight presidential vote * Mexican midterm vote shows Lopez Obrador loses super-majority * Peruvian stocks tumble 7%, set for worst day in 15 months (Adds comments, bullets, details; Updates prices throughout) By Shreyashi Sanyal and Susan Mathew June 7 (Reuters) - Peruvian assets were slammed on Monday as socialist Pedro Castillo overtook right-wing rival Keiko Fujimori in the country"s presidential election vote count, while Mexican markets cheered early results of midterm elections. Peru"s sol currency fell as low as 2.8% to a record low of 3.9370, while its stock index tumbled 7.2%, on track for its worst session since March 2020 after Castillo took the lead against Fujimori in the official tally on the back of a late surge of rural votes, with over 94% of the vote counted. The final result may not be known for days, but Peru"s currency and bonds have suffered since Castillo scored a surprise first-round win back in April on promises of more state control of the country"s mining, energy and telecoms industries. "The tight race and a fragmented Congress suggest that either candidate could face governability issues," said strategists at Citi. "Uncertainty around results should preclude a rally in asset prices in the immediate aftermath, as we wait for a final vote count to come." Mexico"s peso hit a four-week high, while the Ipc stocks index jumped 2%, hitting 2017 highs. Assuaging fears, President Andres Manuel Lopez Obrador"s MORENA party lost some of its majority, the weekend vote showed, which would have allowed him to push through more wide sweeping changes to market friendly policies. Monday"s gains helped the peso wipe away its losses this year and move up 0.3%. Brazil"s real was flat after one of its best weeks this year. Forecasts for Brazil"s growth and inflation in 2021 rose to new highs, a survey of economists showed on Monday, with inflation moving further above the upper limit of the central bank"s target range for the year. But despite the ninth consecutive rise in the inflation outlook, economists" view on interest rates was unchanged. Chile"s peso rose 0.5% despite falling prices of its biggest export, copper. The central bank on Monday said Chile posted a trade surplus of $1.314 billion in May, as the value of copper exports surged. "Market pricing of Latam rate curves foretells tighter monetary policy settings over the next year. ... The state of inflation will also be notably different in a year"s time, thanks in large part to base effects," said Sacha Tihanyi, head of emerging markets strategy at TD Securities. "We see the benefits of these shifts substantially accruing to BRL, and to a lesser degree, MXN. On the flip-side COP will encounter difficulties, but CLP in particular will face very challenging headwinds, even more so considering current valuations." Key Latin American stock indexes and currencies at 1905 GMT: Stock indexes Latest Daily % change MSCI Emerging Markets 1381.27 -0.02 MSCI LatAm 2696.79 1.18 Brazil Bovespa 131072.97 0.73 Mexico IPC 51549.41 2.11 Chile IPSA 4163.57 -1.47 Argentina MerVal 67544.80 2.047 Colombia COLCAP 1245.44 -1.02 Currencies Latest Daily % change Brazil real 5.0325 0.06 Mexico peso 19.8194 0.69 Chile peso 715.1 0.41 Colombia peso 3605.25 0.00 Peru sol 3.9368 -2.46 Argentina peso (interbank) 94.9700 -0.11 Argentina peso (parallel) 154 1.95 (Reporting by Susan Mathew and Shreyashi Sanyal in Bengaluru; Additional reporting by Aaron Saldanha; Editing by Jonathan Oatis and Alistair Bell) Our Standards: The Thomson Reuters Trust Principles.