(CNN) Dick Uilhlein, one of the top Republican megadonors nationwide, has decided to back Ted Cruz's presidential campaign and has donated $1 million to his super PAC.

Uilhlein committed on Wednesday evening, according to Drew Ryun, a super PAC official with Keep The Promise PAC.

"He is one of the top five courted GOP donors," Ryun told CNN. "For us to land him is a good shot in the arm for Ted, and it really sets the stage going into Iowa."

Uilhlein previously backed Scott Walker's campaign and gave $2.5 million to his super PAC.

Uilhlein, of Illinois, started the shipping line Uline.