Texas Rep. John Culberson said Cruz is "committed to restoring the America we know and love."
It will be one of his first appearances since Hillary announced her campaign.
Hillary Clinton is in a hurry to boost her appeal among liberals.
The former Texas governor compared a trio of potential GOP rivals to President Obama in 2008.
Unintimidated PAC is made up of former aides to the Wisconsin governor ahead of a 2016 bid.
After Iowa, she'll hit the Granite State next week, which helped her make a comeback in 2008.
But the former Republican later backed off comments he made in two TV interviews.
Former president said he told his younger brother he hoped he would win "but I don’t know."
"They have always stood for freedom," he wrote of the conservative donors.
The tribute comes amid calls for a more progressive primary challenge to Clinton.