Well is we look at the votes from the 1936 general election in which 10 million voted; the Leftist groups commanded 4.7 million votes to the Rights (Nationalists) 4 million votes. While groups in the Centre managed to get about 500,000. Yet roughly 30% of the eligible voting population abstained.

The Spanish Civil was very complicated. With people later switching sides during the war over the Republican forces becoming overly radicalized by Communism so you could argue that the nationalists had more support toward the end of the war.

This election is what directly caused the war. As the left gained 267 deputies to the rights 132. This huge margin in the lefts favor angered the right. Who had lost the election by and extremely narrow margin. Leading them to stage a coup.