Tonight’s opening of the Democratic National Convention in Chicago will be an opportunity for the Democratic Party and the nation to take stock of Joe Biden’s term of office and thank him for his service. He still has five months to go as president, of course, but the baton has been passed. Biden’s singular achievement has been to change the economic paradigm that reigned since Reagan and return to one that dominated public life between 1933 and 1980 — and is far superior to the one that has prevailed since. Biden’s democratic capitalism is neither socialism nor “big government.” It is, rather…