Broken promises explain drop in Bolsonaro’s approval rate

In just two months, Brazilian President Jair Bolsonaro has managed to do something that has taken past presidents years: losing 15 percentage points in popular support. The rate of voters which consider his administration as doing a “good” or “great” job has gone from 49 percent in January, to 39 percent the following month—to just 34 percent now. Meanwhile, the administration is rated “O.K.” by 34 percent, with one-quarter of voters placing Mr. Bolsonaro’s performance as either “bad” or “terrible.”

While the numbers show that there are still more voters supporting than throwing rocks at Jair Bolsonaro, he is also seeing the worst early approval rates of any first-term head of state. The numbers in his third month since taking office are only higher than those registered by Fernando Henrique Cardoso and Dilma Rousseff at the beginning of their second terms. But in both cases, that was following years of wear and tear—and voter disappointment following failed campaign promises.

In 1998, Mr. Cardoso won re-election by...