Beagle Back to the WWII thing for a sec.
First off, as has been noted above Liberals != Socialists != Communists != Leftists. If you want to say that the first three fall under the blanket category of “Leftists” than so be it, although the loss of precision should be enough to make any honest advocate blanch.
Liberals, led by their patron saint Franklin*, were ahead of the curve anti-Hitler wise (if only because of FDR). Lend lease, various modifications of the neutrality act, arming of merchant ships - all went through a democratic congress (where the president’s liberal wing took the lead). Saving England/Europe from Hitlerism/Naziism - priority for the liberals.
American Communists, led by Soviet tools, were anti-Hitler up until Molotov-Ribbentrop, then neutral/anti-interventionist on the German question, until June 22, 1941, when they saw the light, which no doubt arrived via telegraph from Moscow.
Conservatives, especially Republican conservatives, were well behind the curve. I believe the 1940 campaign involved FDR mocking the isolationists (Martin, Barton and Fish?), stealing their support from beneath them. Certainly Lindbergh and the America Firsters were waaaaaaaaay behind the curve. In general, the (conservative) isolationists contemplated war only after December 7th, and then mostly against Japan. If I consider the America Firsters conservatives and therefore “rightists”
So to summarize:
Liberals: Anti-Hitler
Communists: Soviet tools - not anti Hitler 'til 6/41
Leftists: No one position
Conservatives: Isolationist
America Firsters: Pro Hitler 'til 12/41, then silent
Rightists: No single position, but on board the anti-Nazi train a heck of a lot later than leftists, 'specially liberals
*FDR was undoubtedly an elite. He was considered a traitor by his fellow elites for going over to the liberal/democratic side when they remained Republican