This summer, Venezuela was poised to assume the rotating presidency of Mercosur, a trade bloc that includes Brazil, Argentina, Paraguay and Uruguay. But at the urging of Paraguay, Mercosur heads of state are considering blocking Venezuela, at least temporarily, citing the erosion of democracy there.

This shows that neighboring countries are starting to take a harder line against Venezuela’s president, Nicolás Maduro, whose authoritarian and reckless policies have plunged his country into economic and political crisis. It follows a hearing last month at the Organization of American States in Washington during which Secretary General Luis Almagro criticized Mr. Maduro for using the courts, which he packed with allies, to thwart the opposition-controlled parliament and for arbitrarily detaining political prisoners.

Democratic governance is a requirement for Mercosur membership. The bloc briefly suspended Paraguay in 2012 over the impeachment of President Fernando Lugo by its Congress, which some regional leaders saw as a coup. Paraguay now argues, with good reason, that Venezuela’s disregard for democratic principles cannot go unaddressed.