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Senator Ted Cruz of Texas often casts himself as the rightful heir to Ronald Reagan’s mantle of conservatism, and on Wednesday he took a page directly out of the former president’s playbook.

By tapping Carly Fiorina to be his running mate, Mr. Cruz becomes the first presidential candidate since Reagan to name a vice-presidential pick without having the nomination locked up. In 1976, Reagan teamed up with Richard S. Schweiker, a Pennsylvania senator, in a desperate attempt to grab the nomination from President Gerald R. Ford as it was slipping away. At that point, Mr. Ford’s delegate lead had become virtually insurmountable.

“It was seen as an important move in the sense of giving some vitality to the campaign at that time,” said Edwin Meese III, who was a senior adviser to Mr. Reagan that year. “We had kind of run out the string of things to do in terms of what would generate news and keep the campaign in the news.”

Mr. Meese, who was in the meetings when the strategy was settled upon, said the campaign hoped that Mr. Schweiker could help deliver uncommitted Pennsylvania delegates to Reagan and serve as a bridge to Congress for him. While the tactic did draw significant attention, Ford ultimately won the nomination and then lost the election to Jimmy Carter.

The contours of the strategy are similar for Mr. Cruz. The Texas Republican is in dire need of momentum after having lost five states on Tuesday, and he will need a spark to keep alive the possibility of blocking Donald J. Trump from winning the 1,237 delegates needed for the nomination. Ms. Fiorina provides Mr. Cruz with a tie to her home state of California, which is the largest remaining delegate prize on the electoral map, and she highlights Mr. Trump’s weakness with female voters.

While Mr. Meese was not inclined to predict whether the strategy would work for Mr. Cruz, he suggested that it probably could not hurt at this point.

“I don’t think Ronald Reagan lost anything by doing it,” he said. “If anything, he gained the objective, which was getting some attention.”