Here is just one key excerpt:
Primaries and caucuses had been around for much of the 20th century, but until 1972, party bosses, not voters, ultimately had the most say in picking the nominees. In 1952, for instance, the Democratic barons selected Illinois Gov. Adlai Stevenson at the convention instead of the popular Sen. Estes Kefauver, who had won most of that year's primaries -- even beating President Harry S. Truman in New Hampshire. Kefauver, who had made his name by holding dramatic televised hearings into organized crime, was too outspoken to get the nod from a smoke-filled room.
The disastrous 1968 Democratic National Convention shattered confidence in this efficient but undemocratic system. Instead of a dove such as Sen. Eugene McCarthy, party leaders from large, non-primary states tapped Vice President Hubert H. Humphrey, who had cravenly supported President Lyndon B. Johnson on the war in Vietnam and had sent surrogates to run in his place in the primaries. Outside the convention, young demonstrators howled in protest and were beaten by the police. Next time around, reformers led by Sen. George McGovern deliberately weakened the role of the conventions, making primaries the determining force in picking presidential candidates. The Republican Party, feeling some of the same frustration, soon followed suit.
Interestingly, as the column points out, the Dems had better luck picking presidents when the "Party Bosses" got to decide ...