Washington (CNN) President Donald Trump is beginning to wonder aloud whether his embattled Veterans Affairs nominee should step aside "before things get worse" and White House aides are now preparing for that possibility, White House officials told CNN.

While the White House was preparing for the possibility Jackson could withdraw, it was not clear Wednesday evening whether Jackson was leaning toward dropping out or pressing forward.

After meeting with GOP lawmakers on Capitol Hill, Jackson returned to the White House.

Jackson emerged late Wednesday from White House spokesman Raj Shah's office with press secretary Sarah Sanders, Shah and deputy press secretary Hogan Gidley.

Jackson told reporters, "Look forward to talking to you guys in the next few days."

Sanders said they were having a "debrief" on the meetings on the Hill.

The President and his aides were openly discussing the possibility that Jackson could pull his nomination, the officials said, and aides late Wednesday afternoon began preparing for a possible withdrawal -- though White House officials said the decision remains Jackson's.

Trump's thinking on Jackson's nomination has been rapidly evolving. Earlier on Wednesday, he raised the prospect of going into the briefing room today to stick up for Jackson, simply to say he is a good guy and has his support.

But several senior administration officials, including Sanders, advised him against doing so.

The fresh allegations appeared to change even the President's thinking, who wondered aloud on Wednesday afternoon whether Jackson should step aside now "before things get worse," an official said. Trump was also astonished that few have publicly come to Jackson's defense leading the President to believe Jackson's fate is more perilous than it seemed.

Asked earlier Wednesday evening about CNN's reporting, Shah said aides were "of course" preparing for the possibility that Jackson could withdraw his nomination.

"This is, as the President said, Dr. Jackson's decision," Shah said on "Erin Burnett Outfront." "We stand behind him 100% depending on what he decides to do. We think he'll make a great secretary of Veterans Affairs, but this is a nasty process right now."

Emerging from the White House press secretary's office earlier on Wednesday, Jackson said he would continue to fight on.

"We're still moving ahead as planned," Jackson said, adding denials of several of the fresh allegations, including that he had wrecked a government car after drinking.

But his comments belied the increased skepticism about the fate of his nomination inside the White House. One official conceded the raft of new allegations makes it harder for the White House to provide a defense.

Senate Democrats on Wednesday afternoon released a two-page document summarizing allegations 23 current and former colleagues of Jackson have made against him behind closed doors. Lawmakers have not yet substantiated the claims and are investigating them further, but they included allegations that he was "abusive" to colleagues, loosely handled prescription pain killers and was periodically intoxicated.

Speaking on Capitol Hill Wednesday evening, White House Legislative Affairs Director Marc Short acknowledged the claims of misconduct that surfaced hours earlier caught the administration off guard.

"It appears these allegations were brought to senators and so in some cases all of us are in the dark as to the allegations themselves," said Short, who added he planned to meet with Jackson at the White House on Wednesday evening.

An aide for Montana Sen. Jon Tester, the top Democrat on the Senate Veterans Affairs Committee, pushed back against White House criticism Wednesday, telling CNN that each Jackson allegation in the two-page document came from multiple sources.

"Every allegation in that document has been brought to us by more than one source," the Tester aide said.