Cruz responds to a question about his pledge to support the nominee

Washington Examiner:

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"I am not in the habit of supporting people who attack my wife and attack my father," he said, just hours after his controversial convention speech Wednesday night. He said Trump's attacks against his family invalidate his pledge to vote for the GOP nominee.

"And that pledge was not a blanket commitment that if you go and slander and attack Heidi that I'm going to nonetheless come like a servile puppy dog and say 'thank you very much for maligning my wife and maligning my father,'" he said.
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There is another reason why he was not bound by the pledge.  Trump had already renounced the pledge.  As a matter of basic contract law, someone who renounced an agreement can not hold another party to the same agreement.  When Trump renounced the pledge the others were no longer required to honor the pledge if he became the nominee.