At one point in time the Denver Post was the newspaper with the progressive editorial board.  That was back when there were two major new organizations in town.  When the Rocky went away some of the conservative editorial columnists moved to the DP and the character changed from progressive to a broader spectrum.  Even when the DP was the progressive paper their conservative publisher would at times put his thump on the scale.  Now that the paper is controlled by a PE group mostly intent on what they can suck out of the venture before capturing the tax advantage when closing it down who knows what editorial position they take.
Any editorial page that give voice to John Carroll and the Independence Institute is not left wing.