Unless Mitt Romney issues a direct repudiation of Donald Trump and his doubling down of birtherism, it could hurt him politically. Could it be the 1964 Lyndon Johnson vs Barry Goldwater election in which Johnson won 90% of the vote? I'd say no regarding that big a margin of defeat. The reason I'm bring up the 1964 election is because there was a political decision during that election that the Republican Party and conservative leadership had to make. Today we have birthers. More than 45 years ago it was the it was the communist conspiracy promoting John Birch Society. William F. Buckley along with the Republican leadership banned the John Birch society from the mainstream of conservative politics.
Buckley republished a portion of his 5,000 word repudiation he gave of the John Birch Society in 1964:
How can the John Birch Society be an effective political instrument while it is led by a man whose views on current affairs are, at so many critical points . . . so far removed from common sense? That dilemma weighs on conservatives across America. . . . The underlying problem is whether conservatives can continue to acquiesce quietly in a rendition of the causes of the decline of the Republic and the entire Western world which is false, and, besides that, crucially different in practical emphasis from their own.President Obama is wasting no time using this to slam Romney being so friendly to Trump.