McGovern was seen as a crazy leftist
Even that is under-statement. A lot of people seriously questioned the man's sanity. Nixon didn't have to campaign at all for that election.
I remember watching an All in the Family episode where Meathead inherited $400 and donated it to the McGovern telathon because the Democrats didn't have enough money: now that's just sad if it's true.
Well, it's realistic. This was the last Presidential election before the current system of partial public fianancing for campaigns came into effect. Nixon vastly outspent McGovern in the campaign, the last one in which both parties didn't have equal amounts of money to spend after the conventions are over as is the system today.
It's also worth remembering that McGovern's election showing was obviously harmed greatly by Watergate. He still would have lost by a decent margin even without it (which is why it was particularly stupid for Nixon to do what he did; I guess he wasn't satisfied with just a large victory, he absolutely had to have a massive win), but it helped turn him into an embarassment.
