Contrary to popular belief, the Republic's election results shifted to the right after only two years. Ironically, one of the reasons for this was the enfranchisement of women, who in Spain during this era favored the right (something lefties today don't like to mention much for some reason). This didn't matter though, because the left kept exploiting loopholes to remain in power as much as possible and undercut any power the right rightfully gained. They repeatedly denied CEDA (the right wing coalition) its right to form a government. The Republicans should be called "Republicans" in scare quotes, because they represented republican government in name only, especially once they sided with the commies and anarchists, who had already tried to overthrow the elected government several times.
Commies and anarchists displayed an insatiable lust for Catholic blood during the whole time period of the Republic, starting up anti-clerical violence within the first year. Anyone who tries to tell you that these bastards were only so anti-Catholic in Spain because of the relationship between Catholicism and Falangism (fascism, as they'll no doubt say because that's the scarier word), don't believe the fuckers. That is an exact reversal of cause and effect. Catholics were drawn to Falangism and the Nationalists because of the relentless, violent persecution of commies and anarchists who saw them as easy targets for their spergout rage murder and arson sprees. When the right won elections commies and anarchists murdered people and burned shit, with a focus on priests and churches. When the left won elections commies and anarchists murdered people and burned shit, with a focus on priests and churches.
The left led Republican government constantly dragged its feet to do anything whatsoever about this because these groups were also a major source of support for the Popular Front. By the time the right decided it was time to overthrow the government after years of getting fucked over trying to work within the system, there were already several large parts of the country that were basically in open left wing revolution, which the Popular Front led government was doing absolutely fucking nothing about. But of course once Franco came, these two groups (the Republic government and the far left revolutionaries) set aside their differences and allied to put down the "rebellion."
The Civil War would have been completely different, and a lot less bloody, if these supposedly more moderate leftists in the government had volunteered to work with the right to put down all the violence and criminality from the far left, or if they'd just honored the elections properly in the first place, but that would have meant ultimately losing most of their political power.
Lefties also like to excuse Republican atrocities by casting doubt on whether they were ordered from higher up, because unlike in the Nationalists, the Republicans preferred to go on a system that worked more like this:
But replace demanding twenty bucks with death squads, and the two guys are absolutely in association, but the guy without the gun insists that he can't keep the guy with the gun in check.
The Spanish Civil War was brutal and horrific on both sides, but the "Republicans" were a bunch of two-faced, corrupt bastards their whole time in power who enabled and abetted violent extremists in intense religious persecution and murder, and constantly undermined the representative government they claimed to support. By contrast, after the brief, brutal crackdown period post war, Franco reigned over a lengthy period of peace, stability, law, order, and economic prosperity.