"If asked, the answer is Trump has not made the commitment in writing," Norquist told CNN's "Party People" podcast hosts Kevin Madden and Mary Katherine Ham in a recent conversation.
Norquist continued, "He has to his credit publicly said to Time magazine and out loud, 'I will never support a tax increase' and his tax plan is fine."
Madden followed up, "He's also publicly said things and then publicly said he did not say those things."
"That is why -- and not just for Trump -- that is why we want it in writing for everyone," Norquist said. "So, I'm not going off his verbal statement. We are waiting for the pledge. I do expect that we will eventually get it."
CNN has reached out to the Trump campaign for comment on the pledge and has yet to hear back.
The Taxpayer Protection Pledge, which was launched in 1986, asks candidates for elected office at the federal and state level to sign a pledge promising to never vote for a tax increase. Norquist said more than 90% of Republicans in Congress have made that commitment.
"It's branded the Republican party as the party that won't raise your taxes," he said. "Is that all the issues in the world? No, but it is a central issue and it divides the two parties more than war, abortion, guns. The two parties are completely separated out. There's no Republican that will cheerfully raise taxes and there's no Democrat who won't."
He added, "Republicans have had impure thoughts over the last twenty years, but so far none of them acted on this."
Norquist said he and former Trump campaign manager Corey Lewandowski had communicated earlier this year that Trump would sign on to the pledge, though Lewandowski, who is now a CNN contributor, left the campaign shortly after that conversation.
Norquist pointed out besides Trump, former Florida Gov. Jeb Bush was the only other hold out among Republican presidential primary candidates, which at one point included more than a dozen candidates.
To hear what Norquist thinks of the Republican party's future, how he'd change debates and what the Burning Man festival can teach Americans about liberty, listen to CNN's "Party People," a new podcast from CNN where a pair of conservative CNN contributors talk to influential voices about the future of conservative politics and the Republican party.
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