I agree that the Democratic Party's economic positions have shifted rightward, and there are big parts of what their poverty, tax and Wall Street positions look like Rockefeller Republicans.
What I think I see is that Nader and Sanders each came after 8 years of Democratic rule, pushing us toward the left after "lesser evil" wins.
Meanwhile the corporate Dems biggest surge ever was Bill Clinton and the "Third Way," which came after 12 years of Reagan and Bush.