Shock and horror, and probably quite a lot of revulsion, this being the seventies and all. I don't know what Thorpe's majority was in '74, but he lost his seat in '79 in OTL after the full impact of Rinkagate had become public, so he may lose it in October, if he's not forced to resign as leader before then.
Interestingly enough, if Thorpe had confessed to his relationship with Scott, then he would technically be confessing to having broken the law as it then was. So I don't really see much chance of Thorpe surviving, whatever he does.