At a rally in Ft. Wayne, Indiana, Fiorina stayed mostly silent while Cruz interacted with the gaggle of press beforehand.
But, when she later took the stage, she proved why she has been such a strong surrogate for the Texas senator.
Cruz was peppered with questions by reporters about whether picking Fiorina simply amounted to an act of desperation, something Trump has claimed.
“Of course he would scream desperate. That is Donald Trump, it’s the only way he knows how to operate," Cruz said. "I gave the [explanation of] why we made the announcement early. It is certainly unusual to make a vice presidential announcement early before the convention. But this, if anything, is an unusual presidential cycle."
“I think Carly is a powerful leader to help unite this party and bring us all together,” Cruz said. "I think it's important for the people of Indiana for the American people to know exactly what you're going to get and to give a clear choice. Donald Trump and Hillary Clinton are virtually indistinguishable on policy issues across the field."
The two further made things official with their first joint campaign ad.
Cruz told Tony Katz in a radio interview that Fiorina was on a short list of 17 candidates that had been winnowed down from 40 prospective choices.
A Cruz campaign source tells ABC News that Carly Fiorina will be "really important" in their efforts in California. Fiorina also will likely hold her first solo campaign event since being announced as Cruz's VP pick tomorrow afternoon.
"She'll fill lots of roles within the campaign. She'll travel on her own. She's going to be really important in California but she's going to do a lot of her own events here in Indiana," the source said. "Tomorrow afternoon she'll go and do some events on her own apart from us."
The Cruz campaign and Fiorina’s team have reportedly been working well together. "She has a team of folks that we've been working with as well and they're great to work with," the source said. "This is about two teams merging together and we'll continue to see that. She had a lot of great people working for her and will be helping us out as well."
ABC News spoke with Indiana voters who attended Cruz’s rally in Fort Wayne Thursday afternoon.
Fort Wayne local Gina Wyatt is an undecided voter, but might consider voting for Cruz now that Fiorina is his VP pick.
"I’m still thinking, but now that he has Carly Fiorina, I like her,” Wyatt, 54, told ABC News. “I think that might pull me in.”
Wyatt said she liked that Fiorina brought a business perspective to the table. “You need a politician, you need a business person,” she said, adding it was good to have a woman on the ticket.
Business owner Paul Schroeder, 55, from Battleground, Indiana, attended the Cruz rally with his wife and six kids.
He said he would vote for Cruz, but that Ben Carson had been his first choice originally.
"I’m not sure she would’ve been my first choice,” Schroeder told ABC News. “But I think she’s a great running-mate for the ticket.”