Biden was knocked out of contention for the Democratic Nomination in 1988 because he copied a speech delivered by British Politician a year earlier (and even went so far as to fudge his own familly history a bit to make the copied lines work)
That hardly seems like plagiarism, more paraphrasing and even then it isn't like he took the entire speech - just a basic idea and two sentences (which he apparently cited everywhere except once).
http://en.wikipedia.org/wiki/Joe_Biden_presidential_campaign...