Ted Cruz has said Rupert Murdoch uses his newspapers to choose the prime minister of the United Kingdom.
The Republican presidential candidate, whose attempt to stop Donald Trump clinching his party's nomination could rest on the result of Tuesday evening's primary in Indiana, said "media executives" were backing Trump.
"Rupert Murdoch is used to picking world leaders in Australia and the United Kingdom, running tabloids, and we're seeing it here at home, well the consequences for this nation," he said.
"There is a broader dynamic at work, which is network executives have made a decision to get behind Donald Trump. Rupert Murdoch and Roger Ailes at Fox News have turned Fox News into the Donald Trump network, 24/7."
Cruz, a senator from Texas, said the media was "trying to convince Americans the race is decided".
"The people of Indiana can prove that wrong. And the country is depending on Indiana. If Indiana does not act, this country could well plunge into the abyss. I don't believe that's who we are. We are not a proud, boastful, self-centered, mean-spirited, hateful, bullying nation," he said.
Trump looks set to win the primary in Indiana tonight, setting him on course to clinch the delegates needed to secure the nomination.
The HuffPost Pollster average shows Trump leading Cruz by 14 points, 43 percent to 29 percent. Trump leads in almost every poll, by margins ranging from 5 points to 17 points.