Donald Trump will not push for investigations into former Secretary of State Hillary Clinton for her use of a private email server or for the business practices of the Clinton Foundation, a Trump senior adviser signaled Tuesday.

A source with knowledge of the decision told MSNBC's Morning Joe that president-elect Trump won't pursue the probe that he promised supporters during the campaign, a move that Trump senior adviser Kellyanne Conway appeared to confirm during an interview on Tuesday morning.

"I think when the president-elect ... tells you before he's even inaugurated he doesn't wish to pursue these charges, it sends a very strong message, tone and content, to the members [of Congress]," Conway said. "And I think Hillary Clinton still has to face the fact that a majority of Americans don't find her to be honest or trustworthy, but if Donald Trump can help her heal, then perhaps that's a good thing."

The president of the United States is not the one who unilaterally chooses to launch or not launch a criminal probe. But the announcement is still a reversal of a key - and highly unusual - pledge that Trump made repeatedly during his campaign.

Throughout the general election, Trump promised to appoint a special prosecutor to investigate Clinton's emails, and his supporters regularly chanted "Lock her up!" at his rallies.

During one of his debates with Clinton, Trump told her: “If I win, I am going to instruct my attorney general to get a special prosecutor to look into your situation further."

Trump himself hinted that he was prepared to walk back the pledge during his first post-election interview earlier this month.

"They're, they're good people," he said of the Clintons during an interview on "60 Minutes." "I don't want to hurt them."

On Tuesday, Conway also indicated that Trump would consider adding a Democrat to his cabinet, which would be a reversal of Trump's stated position last month.

"I think the answer is yes," she told Morning Joe.