The people who supported the nationalists were very few in number, virtually none of the working class.
Ok. Wow. That is quite the claim. Geographically and statistically, yes, the Republicans at the outset of the war numbered more people in their territory than the Nationalists. But that doesn't tell the whole story. People supported both sides for lots of reasons, including just literally being in a Nationalist or Republican area when the war broke out. It is nowhere near as clear cut as that.
Despite the result of the 1936 elections being pretty neck to neck, the establishment will 'always' have a significant advantage against the underdog. The campaign expenditure for the nationalists was 5 times more than the Republicans, and yet the Popular Front still won. Most people voting Nationalist did so sub-consciously and in the spur of the moment, and would most definitely have withdrawn any support they'd had for them when they rounded up, tortured, and shot civilians as well as seeking to end democracy. Nationalist soldiers in most cases fought because they didn't have a choice.
This is
really loaded analysis. You ignore the religious, the Carlists, the fervently anti-socialist, the traditional, and all sorts of other motivations for joining the Nationalist cause. You can't in good faith claim that all these people were tricked or duped into doing what they were doing, it just isn't that simple. Besides, equating the election with support in the Civil War isn't a good comparison - a decision to vote and a decision to take up arms are very different. Its worth pointing out that many on the Republican side were horrified by the outrages of the militia and others in desecrating churches, shooting political enemies, etc. And a good deal of Republican soldiers were conscripts, especially as the war went on.
An election is also just snapshot of actual public opinion, and only around 70% of the population voted at all. It is similar to modern elections, why do people so often vote against what is in their best interests by voting Conservative in Britain for example? It's because lots of people aren't invested in politics, and these tend to be the people who either don't vote, or vote how they are told to vote by the establishment.
I really don't think you can equate this with voting in the present day UK, and to be honest your understanding of why people vote Conservative [they are stupid or tricked or both] is pretty insulting. People vote for all sorts of reasons, and popular conservatism has been a major part of modern Britain. Think about this - the Conservative Party was in power for the majority of Britain's c20th during a period where up to the 1980s the vast majority of the population described themselves as working-class and to vote Conservative would have been, in your analysis, 'against their best interests'. Do you really think that for the majority of elections in British history the Conservatives have simply been able to dupe people, or is it more likely that some working-class people were genuinely won over to the cause?
However, military coups and the threat of dictatorship almost always unite the populace overwhelmingly on the side of democracy.
OP - the very Civil War you are talking about disproves that statement. This is the conflict that gave us the very term ''Fifth Column'' the idea that a place behind your own lines, in this case Madrid, would harbor a significant number of the populace actively prepared to overthrow your regime. Yes it was a propaganda ploy by the Nationalists, but contemporary accounts talk of plenty of pro-Nationalist groups behind Republican lines in Madrid, Valencia, and even Barcelona.
During the July Days, there was major conflict between the right wing Republican government and the grassroots CNT, UGT, and POUM. Barcelona more than anywhere had completely abolished capitalism, and destroying the communes and re-asserting government and capitalist control greatly demoralised the Republican cause. The working classes overwhelmingly supported the CNT and collectives, and had the POUM managed to persuade the CNT, UGT, PSOE left, and the Socialist and Libertarian Youth organisations, they would have had complete support from the populace, who wanted to completely do away with capitalism to a greater or lesser extent depending on area.
But you haven't answered by basic question of HOW. Yes, if the POUM could get every other major left-wing faction to support them they could gather a united front [although this would mean compromising their own ideology as part of a coalition] but that is like saying that if Bernie Sanders had been able to get every faction of the Democratic Party behind him he would have won the primary. Yes, of course he would, but the question again remains HOW would he do that, particularly as OTL many factions had no interest in supporting his agenda as it stood. This is before you even tackle how a POUM left-coalition would take power from the current Republican Government. Uprising? Coup? Further dividing the fragile defence of the Republic?
The lack of arms from the Soviet Union would be a disadvantage yes, but the USSR in doing that made it conditional on essentially maintaining capitalism in Spain. Weapons were withdrawn from the populace post 1937 and only given out to the official Republican army. When numerous leftists have been tortured and executed by the side you are fighting for, what difference does it make who's side you're on if they're both the same? This is the conclusion many made and it led to many desertions.
If the Communist International refused to help the Spanish, they would be exposed and Stalin would be considered a traitor to the revolution. If initially International Brigades are set up, I doubt the whole thing would just stop if the Kremlin withdrew its support, rather support for the Kremlin would dwindle.
Just to be clear we are talking about 700 tanks, 300 armored cars, 500,000 rifles, 29 tonnes of ammo, etc etc. This isn't a disadvantage, its a disaster. 1000 qualified and trained pilots, for example, and the tutors to train more as well as the c250 planes they flew. That basic stat alone should terrify you, it makes the Nationalist advantage in the air go from ''superior'' to ''overwhelming''. The Condor Legions terror bombing can go completely unchecked, shattering Republican Morale.
You are misunderstanding my post. Without the Comintern supporting the war effort, which won't happen if the POUM purge the PCE from their side, their WILL BE NO INTERNATIONAL BRIGADES. The entire thing was a Communist project. You'll get a trickle of volunteers coming anyway, but nothing like the organized flood of recruits, trained officers, and prestige.
Also don't underestimate how easy it would be for Stalin to wash his hands of Spain and still retain goodwill on the International stage among left-wing groups. Communist Parties across Europe basically were run from Moscow in this period - the PCF, much bigger than its Spanish counterpart, willingly endorsed the Stalinist line in all matters. Stalin can wring his hands and say ''Well, isn't it awful. We're abiding by the rules of the Non-Intervention committee like Britain and France and we stand together denouncing the aggression of Italy and Germany in killing civilians in Spain. I'm sure the small shipment of medical supplies we sent in accordance with the non-intervention rules will help and shows our solidarity with Spain's workers. Internally, he can point to the POUM and say 'See, this is why you can't trust Trotskyists and Anarchists. Instead of putting all their efforts into fighting the rebels they are busy purging the small and inoffensive PCE that was trying to fight by their side'. There will be a little backlash internationally for sure, but not anywhere near what you think, and that still doesn't make up for all that lovely equipment from Russia not coming to your POUM.
If the Navy swoops in at the start of the war to destroy the Moorish invasion, then the rest of the war would have been much easier for the Republicans, as they really only have to deal with Castile and western Spain, which is isolated and surrounded. If the POUM had followed the approach of the PCE with a centralised army, but fought the war on an anti-capitalist basis, that would have bolstered morale considerably. They also could have produced their own ammunition factories in Spain, rather than the USSR making them entirely dependent on their aid.
I mean, yes, this is often one of the ways it is argued the Republic could have won, but nothing in your scenario suggests
why the navy is more active ITTL, nor deals with the bigger problems of intervening with the Army of Africa's transfer - such as the British naval ships that actively shielded the nationalist vessels from Republican fire at several points.
The key problem here is that it really wasn't insufficient will to fight that caused the Republican defeat. There were a lot of problems - strategic, logistical, international, and, yes, political - that your scenario doesn't address.