If the failure of the original coup had made Germany and Italy more reluctant to support the Nationalist cause and had not provided the ships and aircraft necessary to transport the Army of Africa from Morocco to mainland Spain, the Nationalists would still have controlled much of the original territory they’d seized at the start of the civil war but would have lacked the heavy weapons and experienced troops of the AoA with which to push towards Madrid. They’d also have lacked the colonial troops who spread absolute terror not only in Republican areas but in loyal Nationalist territories as well.
If that was the case, and assuming that aid from Germany and Italy would be either not forthcoming or would be substantially less, then the Republicans would have most likely ground down the Nationalists and eventually won the civil war. Even before the civil war between the Nationalist and Republicans had been concluded however, the simmering civil war between the Republican factions would have erupted into open fighting; a Second Civil War. Historically, not even the threat of extermination at the hands of the Nationalists was enough to prevent fighting between the Communists, Marxists and Anarchists. (The 1936 Spanish parliamentary elections are truly unique; where else have voters been urged to vote Communist to prevent a Marxist takeover?)
In that situation the Basque and Catalan regional governments would both have stood a very good chance of seceding. It would have also given them the motivation to move for independence rather than just regional autonomy.