It happened earlier this month, but it's worth noting: Gary Johnson won a nine-week legal war for the right to appear on Pennsylvania's ballot. His Libertarians had put in more than enough signatures, more than 20,601, to keep Johnson on. (Major-party candidates only need 2,000 signatures.) His opponents were, mostly, Republicans. And those Republicans managed to clear one other candidate off the list.
Source: Slate. Read full article. (link)