Sen. John McCain's Republican primary challenger Kelli Ward attacked him over his age Thursday, arguing that he is too old and "weak" to serve in the United States Senate.

When pressed by NBC's Chuck Todd Thursday on if she'll support McCain if she loses next week's primary, she said that she probably would, but went on to predict her own victory instead. She said that McCain has "fallen down on the job" and gotten "weak" on the eve of his 80th birthday.

"I probably will [support him if I lose]. We'll see, we'll see. But I don't plan to lose the primary or general. I'm actually the only Republican who can win in the general election," Ward said before making age an issue. "John McCain has fallen down on the job. He's gotten weak. He's gotten old. I do want to wish him a happy birthday. He's going to be 80 on Monday, and I want to give him the best birthday present ever — the gift of retirement."

Todd asked her twice about bringing up McCain's age.

"But you brought up his age," Todd told her. "That's a tough attack."

"Well, I'm a physician," Ward said. "I see the physiological changes that happen in normal aging in patients again and again and again over the last 20-25 years. I do know what happens to the body and the mind."

"So you feel comfortable diagnosing him on air like this?" Todd asked.

"Diagnosing him as an 80-year-old man? Yes I do," she responded.

McCain is the heavy favorite to win next Tuesday's primary contest and take on Rep. Ann Kirkpatrick. According to the latest CNN/ORC poll, McCain leads Ward by a 26-point margin (55-29 percent).

The senator's mother, Roberta McCain, is 104 years old.