“Who would go and be credible with Donald Trump, so that he would listen?”

The Watergate scandal overlapped with late stages of the Vietnam War, which had bedeviled both Nixon and his Democratic predecessor, Lyndon Johnson. In that era, Congress was more powerful in relation to the executive branch than it is now, with more leaders of national stature, several experts suggested.

Kathleen Hall Jamieson, director of the University of Pennsylvania’s Annenberg Public Policy Center, suggested that with the death last year of Arizona Sen. John McCain, there’s no Republican currently in Congress who could replicate Goldwater’s 1974 role.

“Who would go and be credible with Donald Trump, so that he would listen?” she asked. “Mitt Romney? Mitch McConnell? Lindsay Graham? Trump will turn on any of them the minute they say something uncongenial.”

A key then-and-now difference, Jamieson said, is that Goldwater represented the same conservative constituency as Nixon and conveyed the message that Nixon was losing its support.

Trump, she said, has a different relationship with his base than Nixon did with his: The base is loyal to Trump personally, rather than to a party establishment.