All week Mitt Romney has quoted one of his favorite TV series to punctuate the poignant stories of lives cut short that he has woven into his campaign speeches.

Already this week Mr. Romney has stopped mentioning Glen Doherty, a former Navy SEAL killed in the attack on an American consulate annex in Benghazi, Libya, after Mr. Doherty’s mother objected to the candidate politicizing her son’s death.

The “Friday Night Lights” television show, about a high school football team, won critical acclaim and passionate fans, but low ratings during its five seasons on NBC, ending last year.

But on Friday the creator of the series, “Friday Night Lights,” accused Mr. Romney of plagiarism for adopting the slogan, “Clear Eyes, Full Hearts, Can’t Lose,’’ and asked him to stop using it.

“Your politics and campaign are clearly not aligned with the themes we portrayed in our series,” Peter Berg, the writer-director of the show, wrote in a letter to Mr. Romney.

“The only relevant comparison I see between your campaign and ‘Friday Night Lights’ is in the character of Buddy Garrity – who turned his back on American car manufacturers, selling imported cars from Japan.”

The Romney campaign did not immediately respond to a question about whether it would cease using the slogan.