Dr. Phil’s decision to call it quits last week came months after producers tried and failed to revamp the long-running CBS daytime show in a desperate bid to lure back skittish advertisers, The Post has learned.

Phil” amid concerns by viewers that he was lumped in with other “quack doctors” who have left TV in recent years.A decade ago, top corporate brands that backed “Dr.

But during an episode last week, commercial breaks were ridden with spots for vitamin supplements, personal-injury law firms, public-service announcements on vaccines and quitting smoking — as well as multiple in-house ads for other CBS shows.

Ratings for Oz — who had run into his own controversies over pushing alternative medicines and fad diets — had begun to tank even before his candidacy for the Pennsylvania seat.

McGraw — who got his big break on “Oprah” 25 years ago, charming audiences with his folksy takes on social issues — said his next chapter will focus on a “strategic primetime partnership” that will “increase his impact on television and viewers.” He didn’t mention problems with advertisers in announcing his decision to leave.

“I am compelled to engage with a broader audience because I have grave concerns for the American family, and I am determined to help restore a clarity of purpose as well as our core values,” McGraw said.