Last Updated Apr 27, 2016 5:27 PM EDT
Ted Cruz announced Wednesday afternoon that he has chosen Carly Fiorina to be his running mate in the 2016 presidential campaign.
"After a great deal of time and thought, after a great deal of consideration and prayer, I have come to the conclusion that if I am nominated for president of the United States that I will run on a ticket with my vice presidential nominee Carly Fiorina," Cruz announced at a rally in Indianapolis.
"She is careful, she is measured, she is serious," Cruz said. "She doesn't get overly excited, she doesn't get rattled by whatever is thrown at her."
The Texas senator acknowledged that it's unusual to make such an announcement so early, especially before July's Republican National Convention in Cleveland.
"Where we are right now: Nobody is getting to 1,237 delegates. I'm not getting to 1,237 delegates and Donald J. Trump is not getting to 1,237 delegates and the Hoosier state is going to have a powerful voice," Cruz said.
He said he's making the announcement now so that voters in states that have not yet held their primaries know what they will get.
"You deserve to have a candidate who doesn't change to where the wind blows at the moment. You deserve to know exactly where a candidate stands."
Fiorina said she was "very proud, very humbled and honored" to accept Cruz's offer. She said that Trump and Hillary Clinton would both be "disastrous for this nation."
"Donald Trump and Hillary Clinton are two sides of the same coin," she said. "They're both liberal. We know that."
Fiorina then began singing a song from the podium to Cruz's daughters.
"I know two girls who I just adore. I'm so happy I can see them more. 'Cuz we travel on the bus all day, we get to play, we get to play," she sang.
Cruz said Carly often makes up songs to sing to his daughters Caroline and Catherine and texts with them with "heart and smiley-faced emoticons."
In the morning, Cruz teased the news, saying he had a "major announcement" to make later in the day. This comes just two days after a source close to Fiorina, the former CEO of Hewlett-Packard, confirmed to CBS that Cruz was vetting her as a vice presidential candidate. This also comes ahead of Indiana's primary on Tuesday.
Donald Trump called Cruz's decision "a pure waste of time" in a statement before the announcement.
"It reminds me very much of the already failed Kasich "collusion" - a desperate attempt to save a failing campaign by an all talk, no action politician. The people of Indiana are very smart - they will see through this just like they saw through the already failed Kasich alliance," Trump said. "Cruz has no path to victory - he is only trying to stay relevant."
Fiorina endorsed Cruz last month. Cruz has decided to team up with John Kasich to try and block Donald Trump from receiving the GOP nomination.
But the announcement comes a day after Donald Trump expanded his primary lead in the path to the nomination, sweeping all five states that held primaries on Tuesday. According to CBS News' latest count, Trump has 949 delegates, Cruz has 556 and Kasich has 152. A candidate needs 1,237 in order to win the GOP nomination.
CBS News' Major Garrett contributed to this report.