U.S. Republican presidential candidate Ted Cruz, in a last-ditch bid to slow front-runner Donald Trump's momentum, on Wednesday named former business executive Carly Fiorina to be his vice presidential running mate if he wins the nomination.

After suffering a series of crushing losses to Trump in nominating contests on Tuesday, Cruz praised Fiorina as a principled fighter for conservative values who knew how to create jobs and would be a valuable ally on the campaign trail.

"She is careful. She is measured. She is serious," Cruz said. "She doesn't get rattled."