If you think the Democrats wouldn't shaft their own candidate, here's what happened to McGovern in '72:
"McGovern was probably the most radical candidate to run for president on a major party ticket in the 20th Century. Among other items, he called for an immediate end to the war in Vietnam, a guaranteed annual income for all Americans, and reproductive choice for women. He won the series of primaries and was nominated as the Democratic candidate. Before he even gave his acceptance speech, the Democratic leadership was at work sabotaging his campaign. The rules committee played around with floor activities ensuring that his speech would be delivered at 2:00 in the morning. News organizations were provided with unfavorable information regarding his vice presidential nominee’s health. Party conservatives like Henry “Scoop” Jackson (the first neocon) mounted a campaign within the party and in the press designed to prevent McGovern from winning. After the landslide victory of Richard Nixon in November 1972, the party leadership began implementing rules changes that would forever prevent someone like McGovern from gaining the nomination. As Selfa points out, it’s not that McGovern was a radical; it’s that the Democratic Party does not represent the people (who by 1972 wanted out of Vietnam no matter what), but the corporate class."