The ugly truth is that you can be a progressive and be from nearly any point on the American political spectrum – see both Roosevelts, Truman, Ike, Earl Warren, etc.
Of course, if you accept the rhetorical construct promulgated by the far Left – that “progressive” is just a euphemism for “radical” in the way that the far Right uses “conservative” as a euphemism for “reactionary,” then this all falls apart.
In the name of truth and clarity, however, we must reject these political inexactitudes and name things for what they are.
Bernie Sanders is not a progressive. He is a radical. Hillary Clinton is a liberal.
Ted Cruz is not a conservative. He is a reactionary. John Kasich represents something far closer to a conservative. John Huntsman is a conservative with progressive leanings.
And Donald Trump is a power-hungry opportunist who takes on whatever political shadings he thinks will rouse the nearest rabble and get him one more delegate close to election.
We can argue definitions, but let us do so in the quest for accurate descriptions, not for the sake of political spin.