Keep Spruille Braden (the American ambassador) from interfering, since his attempts to stop Perón only made him more popular among the Argentine public. Having the Radical Civic Union pick a different candidate - perhaps Amadeo Sabattini, though he supported Perón in 1946 IOTL - would probably help too.With a POD of July 1943 (a month after Juan Perón took power in a military coup), your challenge is for him to lose the 1946 presidential election.
You can make use of any POD, except for "Perón is removed in a coup and/or is barred from running", that's too easy.
AFAIK Tamborini's platform was pretty similar to Perón's. @minifidel @juanml82But who would substitute him in implementing important policies such as advancement in worker's rights, women's suffrage and, well, introduction of regular television broadcasts in the country?