New Delhi, July 4 -- Brazil's President Luiz Inacio Lula da Silva and his rival Sen. Flavio Bolsonaro clashed over U.S. tariffs this week, as both sought to discourage the Trump administration from following through with its proposal of applying taxes of 25% on Brazilian products despite an extensive U.S. trade surplus.

The two top candidates for October's presidential election traded barbs over their responses, suggesting that they believe how they are perceived as handling the deeply unpopular U.S. tariffs will be a key factor in the vote.

While Sen. Bolsonaro, son of former President Jair Bolsonaro, emphasized that the tariffs would strengthen Lula, Brazil's government rebuked the argument that its trade policies are unreasonable, di...