If he wouldn't scramble from things and effectively plan, execute, and follow-up, he would regain credibility.
The problem is that the Washington Beltway mentality for so long has been about messaging and optics instead of the facts and what they must mean, that even understood problems and mistakes fall into the echo chamber messaging repair cycle. They don't get the look in the mirror and come to terms with the need for getting it right. Instead they just need to deliver a different meassage to fix something in their minds.
...”he would regain credibility”
He cannot regain what he never had. Look at the 1986 tapes from his failed run for President. Same lying, cheating, plagiaristic fake.