Hubbard said his decision is not a sign that he has given up on Walker, who he continues to support. He likened it to investing in multiple companies on the stock market. He said it reflected his belief that there are several talented candidates in a highly volatile Republican primary.
"I'm smart enough to know there could be big changes," he said.
Hubbard said the only super PAC he has given to is one supporting Walker.
Hubbard sees another challenge Walker faces: communicating his message.
"He's got to figure out how to come across on television," said Hubbard.
A Walker spokeswoman did not immediately respond to a request for comment.