Disgraced “CBS This Morning” co-host Charlie Rose was behind the firing of the one colleague who could have stepped into his role on the a.m. show, Josh Elliott, multiple sources said. But Rose says he was only supportive of Elliott.

“CBS This Morning” has been left without an heir apparent to Rose after the veteran anchor was fired for sexual-harassment allegations — and there’s no big-name replacement within CBS News’ ranks to take over. Insiders say it was Rose who, this year, helped get Elliott fired from CBS after he decided the younger anchor was a threat.

A source said, “Josh was ousted by Charlie and his monstrous ego. Charlie flattered Josh to his face, invited him to cover on his PBS show, then stabbed him in the back by issuing an ultimatum to [CBS News President] David Rhodes, who has made a huge mistake. CBS would be in a very different place if they’d kept Josh on . . . They’ve got no big names and nobody to step up and save them amid this crisis.”

Elliott, a former news anchor at ABC’s “Good Morning America,” was dumped by CBS in February after he made an announcement that he was stepping down from CBS’s digital channel after he was promised a correspondent role at the network. Elliott was fired days later by Rhodes, for the fishy reason of “showing bad judgment with his on-air news.” At the same time that Elliott announced his bigger role at CBS, Rose was out recovering from heart surgery.

Threatened Rose felt ambitious Elliott was making a play for his job “at a weak moment,” a source says. “Because of Charlie, they cut Josh off at the knees.”

But now with exposed Rose out, “CBS News shot [itself] in the foot,” says the source. “Josh was the last man on the bench. He had the experience and the talent and could have stepped right up. Charlie is a 75-year-old in failing health who liked to go out at night [and] had a bad reputation. CBS should have seen this coming.”

CBS declined to comment. Rose told us: “Totally untrue. I was very, very supportive of Josh. I loved working with him on [‘CBS This Morning’] and CBSN [CBS’s digital channel].”