Yes, those churches are primarily leftist. What they are not is primarily Christian. Which is why they are hemorrhaging members.
As I've described before here at TBR, Mr. M and I were longtime members of a PCUSA church. Members of the small congregation are very conservative, but the presbytery leaders and the denomination are very liberal. When our whackjob pastor quit in 2013, the presbytery did all it could to make sure we didn't find a conservative to replace him. They sent us a very liberal female interim, who was there for nearly three years. When the pastoral search committee found a good conservative to whom we wanted to extend a "call," the presbytery threw a procedural monkey wrench in the works, halting the process. Mr. M and I finally had enough and left the church because we couldn't continue in that denomination, but the good folks of our former congregation soldier on.
Oh yeah, and the PCUSA is hemorrhaging members like crazy. No wonder.