Regarding Spain, the radical CNT existed in Catalonia since 1910, the moderate UGT has existed since 1888, and two are still working together, more or less (they historically broke when the CNT's radicalism became too much for the UGT to stomach during Primo de Rivera's rule). For political parties, there's the Spanish Socialist Workers' Party, which has been around since 1879. However, in this era before Marxist-Leninism, leftist movements in Spain still tend to be rather anarchic in scope, and also quite weak. Spain really isn't in turmoil yet, either, since the economic collapse of the late 20s and early 30s hasn't happened yet, so you're going to be really, really weak if you do decide to play it like that. Still, if you don't mind wearing the equivalent of a "Shoot Me" sign and doing more or less nothing for a decade or two (assuming economic collapse even occurs), that is a possibility.