It's no coincidence that most of the countries that at some point become more autocratic are presidential republics.

Linz has argued that presidential republics have the following issues:

- dual democracy legitimacy (both president and legislature claim popular mandate)

- rigidity (fixed term rather than parliamentary approval prevents adaptation to crises)

- winner take all logic (total exclusion of opposition from power)

- personalization of power (authority concentration)

Further, the Carnegie Endowment in 2025 found that autocratic transitions occur at "striking speed" in presidential systems.

[1] https://kellogg.nd.edu/sites/default/files/old_files/documen...