(CNN) Decades before President Donald Trump ever attacked the media, Senator Barry Goldwater introduced a new idea to the presidential campaign trail: liberal media bias.

Goldwater was 1964's Republican presidential candidate, and he was convinced that the journalists covering the campaign were infusing their reporting with a left-leaning tilt while claiming to be neutral observers. As a staunch conservative, Goldwater believed this bias put him at a distinct disadvantage in his race against President Lyndon Johnson.

Nicole Hemmer

Struggling in the polls, he insisted that his message — rolling back the New Deal and taking the fight to the communists — was popular with Americans. The trouble, he said, was that his positions were constantly being distorted by the liberal gatekeepers in the media. He needled the journalists trailing him, even handing out pins to reporters that read "Eastern Liberal Press."

Goldwater's "liberal press" claim had some basis -- television news broadcasts and major papers based on the coasts were staffed with journalists who personally tended to support at least some level of desegregation, social safety net programs and US cold war policy -- but they weren't the cause of his uphill battle with voters. Since the end of World War II, Republicans and Democrats had hashed out a rough consensus on many of the major issues of the day — a consensus Goldwater regularly rejected as he adopted positions well outside the mainstream.

It was his fringe position, not the press, that contributed to Goldwater's loss in a historic landslide. Yet even in defeat, he'd pioneered an argument that would become a staple of Republican campaigns: the US media favored Democrats and liberals, and skewed their reporting to help their preferred candidate.

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