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Salem_Saberhagen: The another reason on why 1930 coup happened was that right-leaning people became sick of democratic processes in Argentina as they always lost since Yrigoyen became president in 1916. Do you think UCR would evolve into a center-right party given that there would be competing Socialist Party (in OTL it is limited to Santa Fe province).
I am convinced the 1930 military coup is what completely retarded the proper development of Argentinian democracy and led to the cycle of political instability.
Yrigoyen irritated the Conservatives by abusing the Constitutional resource of "Federal Intervention", under our Constitution the President has power to replace the governor of a province if constitutional guarantees or basic human rights had been violated. However, Yrigoyen used this to remove freely-elected Conservative governors, while Alvear, his UCR succesor as President, was completely respectful of Republican institutions, allowing democracy to function normally even when his party lost provincial elections. This led to the 1920s UCR split between "Personalists" (followers of Yrigoyen who believed he was in the right as leader of the party) and "Anti-Personalists" (followers of Alvear who believed democratic institutions are more important than the whims of a leader).
It is telling that after the death of Yrigoyen the more Conservative anti-personalists became dominant in the party with figures like Alvear, Melo, Tamborini, Ortiz, Mosca and so on. Still, I don't see the UCR going full Conservative, since its roots were in French 19th century "radicalism" (liberalism) with some social democratic leanings.
The party that truly had the potential to become a Conservative bulwark was the Democratic Progressive Party. Despite the misleading name, this party was basically a market liberal party focused on respect for the institutions and anti-corruption. By the 1930s and 1940s it was third in terms of nationwide support and membership, and in the post-coup 1931fraudulent elections it ran in an odd anti-fraud coalition with the Socialists, with the formula De La Torre President (PDP) Repetto Vice-President (Socialist), coming out second in the elections. (And probably first had there been no fraud)
In the 1950s this originally market liberal party veered into a proper Conservative party, but by then its membership had dwindled and its "time in the sun" had passed.
It is likely that had the 1930 military coup not happened, traditional Conservative support would have poured into this party. Instead, the Conservative elites of Argentina got used to using the military as "their party" and knocking the doors of the barracks when things weren't going this way.
After all, the 1930 coup was legitimized by a Supreme Court ruling! Had that not happened the institutions of the country would have been much stronger, the country had gone 70 years with unbroken Constitutional successions and no coups ever before that point.