Palin writes, "Joe is a true Commonsense Constitutional Conservative, and we're thankful he and his family are willing to offer us a choice in Alaskan leadership."
The Miller and Murkowski campaigns did not have immediate comment Wednesday.
Palin beat Murkowski's father, incumbent Gov. Frank Murkowski, in the GOP primary for Alaska governor in 2006. Palin says there's no bad blood between the two. But she believes "we need a bold reformer who is not afraid to stand up to special interests and take on the tough challenges of our time. Joe Miller has stepped forward."