Mexicans are going to the polls on Sunday for the first phase of a dramatic democratic experiment: Replacing the country’s appointed judges with new ones who are elected by voters.

In a single day of voting, the country will select more than 2,600 judges and magistrates, from the Supreme Court to local tribunals, who will make up half of Mexico’s judiciary. The other half will be elected in 2027.

Experts say it is the most significant judicial overhaul ever conducted by a large democracy.

The change was proposed by then-President Andrés Manuel López Obrador, after the Supreme Court and other courts blocked many of his initiatives, and the voting was also championed by his successor and the current president, Claudia Sheinbaum.

Mr. López Obrador and Ms. Sheinbaum argue that electing Mexico’s judges will improve governance and reduce corruption in a country that is plagued by organized crime and violent disorder. The public has little confidence in the existing judiciary: In one recent survey, two-thirds of respondents believe Mexico’s judges are corrupt.

But many experts have warned that this particular overhaul is likely to have profoundly negative consequences — not only for Mexico’s criminal justice system, but for system of checks and balances that are required for a healthy democracy.

The pluses and minuses of elected judges

There are some compelling arguments in favor of electing judges. Like presidents and legislators, they are powerful political actors. The foundational idea of democracy is that the public should be trusted to make choices about how to allocate political power, and that elections are an important way of holding officials accountable. Many judges in other countries are elected, including in 39 U.S. states where voters fill at least some judicial vacancies.