The most reliable verbal maneuver that I have used to flush out a leftist is to ask them; "What do you think will solve our problems?" If they answer "government", "government program" or, in particular, "a strong centralized government", they have shown their red colors. Even a socialist as mild as a Democrat will always answer with; "The Gub'ment aughta' do sumpin' 'bout that!"
The problem with that is that there are problems that the government should address. The chattering classes often talk about 'big' vs 'small' government, but the true distinction is between proper (defense) and improper (socialism) government.
For instance, when it comes to issues of national security, I'll be the first to say, "The gubmint aughta' do sumpin' 'bout dat." That is a legitimate purpose of government.