I don't think everything in The Left's Plan is very popular, and I also get that the (un)popularity of things isn't always as straightforward as polls show, but I also think that The Left in general would be pretty happy if the Democratic party, and especially the supposed moderates, did actually *support those things* even if they were assholes about the less popular/more contentious with voters stuff.
DC brain leads you to think that Fred Hiatt is the voice of sensible moderation, but that's just the Washington Consensus, or I think we call it "neoliberal bullshit" now, and it isn't popular and has never been popular. Argue that it's correct, if you want, but don't claim that it's what Arizona voters are clamoring for.