Brad Parscale’s abrupt demotion Wednesday night “shocked” some inside the Trump campaign, sources familiar with the move told Fox News, even as President Trump’s sliding poll numbers and the recent Tulsa rally debacle had raised questions about his future.

The president announced on Facebook and later on Twitter Wednesday night that Parscale would be replaced as campaign manager by Bill Stepien, who had served as deputy campaign manager.

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Parscale, who ran Trump’s digital operations in 2016 and was promoted to Trump’s right-hand man for the 2020 cycle, is expected to shift back to his previous role.

Two top campaign officials told Fox News that Parscale will serve as a senior adviser focusing entirely on the campaign’s digital operation and data collection.

Speculation has swirled for weeks about Parscale’s future, as Trump has fallen behind Democratic presidential challenger Joe Biden by double digits in multiple polls, and as the campaign struggled to fill seats for the president’s rally last month in Tulsa, Okla.

A source familiar with the situation said that Parscale indeed had been losing influence as of late with other campaign officials exerting more power, including Stepien, who joined the campaign in May as deputy campaign manager after serving as a political director at the White House. There was also the return of Stephanie Alexander, who was on the campaign in 2016 and returned in May as campaign chief of staff.

Still, multiple sources told Fox News that many expected Parscale to stay through the election, and that Wednesday night’s announcement came as a “surprise” and that many were “shocked.”

“They shouldn’t be,” a senior administration official told Fox News. “Had to happen.”

The official added: “This doesn’t surprise anyone who knows POTUS and how he wants his campaign run.”

Stepien, before joining the campaign and the Trump administration, previously managed both of former New Jersey Gov. Chris Christie’s gubernatorial campaigns. Stepien also served as Christie’s deputy chief of staff.

One source familiar with the move told Fox News that Stepien is a "really hard worker," while another said he is "married to his job."

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“Bill’s MO is to keep under the radar and keep his head down and stay focused on the job. So if anything, all the attention he’s gotten probably makes him a little uncomfortable," another Republican operative told Fox News. "He knows his role is to be the guy behind the guy.”

The operative added that the campaign was looking for someone who was a "strong" and "experienced operative."

"Brad is the best in the business when it comes to data, but he’s not a political operative," the operative explained. "Stepien is one of the best political operatives in the country and innately understands data and field and its integration and how to use that to move votes.”

The president announced the shake-up Wednesday night in a statement on social media.

“I am pleased to announce that Bill Stepien has been promoted to the role of Trump Campaign Manager,” the president said in a statement. “Brad Parscale, who has been with me for a very long time and has led our tremendous digital and data strategies, will remain in that role, while being a Senior Adviser to the campaign.”

The president added that both Parscale and Stepien “were heavily involved in our historic 2016 win, and I look forward to having a big and very important second win together.”

"This one should be a lot easier as our poll numbers are rising fast, the economy is getting better, vaccines and therapeutics will soon be on the way, and Americans want safe streets and communities!” the president added.

The move comes as the president’s polling numbers have fallen, with the latest RealClearPolitics average showing Trump trailing Biden by more than 8 percentage points.

The move also comes as the Trump administration has faced immense criticism over the handling of the coronavirus pandemic, an issue that has spilled out onto the campaign trail with Democrats—and Biden himself—hammering the president regularly.

But a major campaign shake-up in the general election for Trump is hardly unprecedented. In 2016, Trump had three campaign managers: Corey Lewandowski, who ran Trump’s primary campaign and was removed ahead of the conventions; Paul Manafort, who ran Trump’s campaign during the convention and then was removed, and is now currently serving jail time for charges stemming from former Special Counsel Robert Mueller’s investigation; and Kellyanne Conway, who led the campaign through the general election to Trump’s victory.

The shake-up follows a similar one less than a month ago, when Michael Glassner, organizer of the president’s rallies, was reassigned, and Jeff DeWit, who served as Arizona chairman of Trump’s 2016 presidential campaign, joined the 2020 staff as chief operating officer.

That change was in response to lower-than-expected crowd turnout at a rally in Tulsa, which embarrassed the president and put the campaign on the defensive. The Trump team noted that the rally attracted large numbers of television and online viewers, and that the coronavirus may have led many supporters to stay at home.

Meanwhile, Biden campaign Rapid Response Director Andrew Bates, in a statement to Fox News, reacted to the news of the shake-up by saying: "Almost 140,000 Americans have lost their lives and millions more have lost their jobs because of Donald Trump's failed leadership. The Trump campaign's game of musical chairs won't fix this. We need a new president for that."

Biden also shuffled his campaign team amid a disastrous stretch in his campaign, albeit much earlier in the cycle. For Biden, the moves marked genuine shake-ups that expanded and changed how the campaign operated.

Biden elevated Anita Dunn, effectively displacing his first campaign manager, Greg Schultz, after a fourth-place Iowa finish and after he was already headed for a second embarrassing finish in New Hampshire. Dunn had joined Biden at the outset of his campaign after having served President Barack Obama as a top communications adviser.

With Dunn’s urging, Biden hired his current campaign manager, Jen O’Malley Dillon, in March after Dunn and others helped resurrect Biden in Nevada and South Carolina and put him on the path to the nomination. Schultz is now at the Democratic National Committee, helping lead the joint battleground strategy among the national party, the Biden campaign and state parties.

Fox News' Paul Steinhauser, Kristin Fisher and Gregg Re contributed to this report.