I don't think it has a specific origin. In a literal sense there are usages from the early 19th century. In the figurative sense you are suggesting it appears to have been used from the first part of the 20h century.
Ngram: further to the right than
From Transatlantic: (1943)
- In the European meaning of the terms, Mr. Roosevelt is certainly further to the " left " than Mr. Dewey, and Mr. Dewey further to the " right " than Mr. Roosevelt. But to use such a distinction without qualification or explanation would be misleading...
From The Twentieth Century : (1950)
- .. it from being regarded as ' conservative.' This last argument was also a reason operating in favour of retaining Liberal co-operation ; for as long as there was still a party in the Government further to the Right than the Christian Democrats, ...
A few usage examples:
Further to the right than Attila:
- I sat to your left, unfortunately, in the happy times when you said I am further to the right than Attila the Hun. That is not true. I respect you for your ability to articulate properly and your integrity and honesty. I truthfully say to you, the Armed ...
(Review of arms control and disarmament activities. 1974)
Furter to the right than Genghis Khan:
- The honourable member for Werribee gave the impression that he was further to the right than Genghis Khan on this issue. I shall quote from the May edition of the Victorian Wilderness News, the headline of which is "East Gippsland Parks (Victoria Parliamentary Debates (Hansard).: Legislative Assembly- 1988)