Why is Brazil once again mired in political chaos?

Less than a year ago, President Dilma Rousseff was impeached and forced out of office in a swirl of claims about financial impropriety. Now her successor, Michel Temer, finds his presidency in peril as well.

Tapes that recently surfaced appear to capture Mr. Temer, who was already under investigation for corruption, approving of bribes paid to a lawmaker who has been jailed for corruption. Many now believe he will also face impeachment.

On Wednesday, Mr. Temer deployed the military in the streets of the capital, Brasília, after thousands of protesters clashed with the police. Although the defense minister said the troops had been sent merely to “restore order,” many saw the move as a sign of profound insecurity from an already weak government.

Political science suggests this is an example of how the “islands of honesty” in corrupt systems — like independent prosecutors and courts with the willingness and authority to enforce the rule of law — can clash with networks of entrenched corruption, both provoking and spoiling efforts by political elites to protect themselves.