McGovern and Mondale; many Democrats (John Connally, along with the Democratic mayors of Philadelphia PA, Warren MI, and Roseville MI) endorsed Nixon in '72.
I don’t think McGovern was a “sacrificial lamb” because he was not the choice of the Democratic Establishment.
The Democrats would be putting up a sacrificial lamb that year whether it was Humphrey, Muskie, or McGovern. Same with 1964, with regards to Goldwater. Even if Rocky or Romney got it instead of Goldwater, they to would be sacrificial lambs.