There never was much to the Left in the United States. Public schools and Social Security are great things, but supporting them hardly makes one a leftist.
Mostly this.
Even George McGovern's campaign has been largely whitewashed as some sort of great left wing crusade against the fascistic Nixonians. Truth is, the only thing that was real radical about him was his Vietnam position (ie, get out now) and his support of reducing defense spending substantially (which at the height of the Cold War, obviously very liberal). Other than that, he was a generic drug warrior for his day who wanted to keep abortion at the state level.
So yeah, kudos to the OP article for pointing out that Mondale campaigned largely as a deficit hawk, but a few points off for acting like it was just some real recent trend for Democratic nominees to "triangulate". That has been going on since Jefferson.