President Jair Bolsonaro of Brazil called dozens of foreign diplomats to the presidential palace on Monday to tell them that he believed the country’s voting systems could be rigged, a potential preview of his strategy for an election that is 75 days away and that polls forecast he will lose in a landslide.

While Mr. Bolsonaro’s presentation was not new — he has repeated those claims for years — his audience was. He had invited officials from most of the embassies in Brazil’s capital, Brasília, elevating his claims from a matter of domestic politics to foreign policy.

He had promised to share evidence that showed fraud in the past two presidential elections, yet much of his 47-minute presentation, which he broadcast to the public, focused on rehashing information about a 2018 hack of Brazil’s elections agency, as well as his accusations that certain Supreme Court justices were trying to sabotage his re-election bid.