Levi Johnston on Tyra Banks show

She knew?

You betcha, says the baby daddy of Sarah Palin's grandson.

The Alaska governor most likely was aware before her daughter, Bristol, became pregnant that the teenager and her hockey hunk boyfriend were having sex, Levi Johnston said in a bombshell new interview.

"I'm pretty sure she probably knew. Moms are pretty smart," said Johnston, 18, the father of the governor's first grandchild, in an interview that will air Monday on "The Tyra Banks Show."