"By the way, she fell off the stage the other day, did anybody see that? And Cruz didn't do anything. Even I would have helped her," Trump told 1,600 supporters while taking swipes at his rival.
In the video, it appears that Cruz didn't immediately see the fall, which did not injure Fiorina.
"That's really cruel," Trump continued. "She just went down. She went down a long way, right? And she went down right in front of him and he was talking, he kept talking. He didn't even look like -- that was a weird deal."
The fall took place in Lafayette, Indiana, while Fiorina was introducing the Cruz family.
With a pivotal vote in Indiana Tuesday, Cruz is vowing to "go the distance," whatever the outcome of tomorrow's primary.
"It is an incredibly important state," Cruz said of Indiana on ABC's "This Week." "We are competing hard. I hope we do well here. I can tell you I'm barnstorming the state, we're in a bus with my family, we're doing everything we can to earn the votes of the men and women in this state. We're going the distance. We're competing the entire distance.”
Cruz, who trails his main rival Donald Trump by hundreds of delegates, enters this week after two weeks of losses to Trump in six states.
Cruz said he is hoping the announcement of Fiorina as his running mate and the endorsement of Indiana Gov. Mike Pence will help him secure a win in Indiana and give his campaign momentum as he heads into other states, including California.