Socialist leader Eugene Debs backed Taft...Perhaps as a political manouver, and I don't know anything about it. As a philosophy, forget it. In fact, many of Debs' closest advisers helped prepare the Bull Moose platform. Debs took almost 900,000 votes that year.
But not his own. He was so busy campaigning elsewhere, particularly in the West, that he failed to register for the election in his home town of Terre Haute, Indiana, and instead spent the election eve at home, celebrating his 57th birthday.
In California, Debs did better thatn Taft, pulling 79,000 votes for his Socialists while Prohibitionist Chafin took 23,000 and Taft managed only 4,000. In Arizona, Debs brought in 3,163, Taft followed with 2,986 and Chafin only 265.
Fyi, in those days, candidates and their supporters were differentiated by colours, often used for backgrounds on campaign buttons and posters and on speech platform bunting. Roosevelt's was Green; Taft's Red. Wilson was White and I'm not certain about Debs, but some of his campaign buttons from that period are a buff-yellow. [I know Seidel was his 1912 running mate; I don't know of a pic of a 1912 Debs button online]