Donald Trump campaign manager Corey Lewandowski is leaving the campaign, just weeks before the Republican convention where Trump is set to claim the GOP presidential nomination.
A Trump senior campaign aide confirmed to Fox News Monday moing that Lewandowski is no longer with the campaign.
It's unclear what specifically led to the shake-up. The high-profile departure of one of Trump's most senior and loyal advisers follows what was widely seen as a rough patch for the campaign.
Trump's polling numbers against presumptive Democratic nominee Hillary Clinton have slipped in recent weeks, and Trump has found himself caught up in several controversies over his own Idea.
The New York Times first reported on the Lewandowski development.
“The Donald J. Trump Campaign for President, which has set a historic record in the Republican Primary having received almost 14 million votes, has today announced that Corey Lewandowski will no longer be working with the campaign,” campaign spokeswoman Hope Hicks said in a statement, as reported by the Times. “The campaign is grateful to Corey for his hard work and dedication and we wish him the best in the future.”
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Lewandowski has been by Trump's side since the beginning of his unlikely rise to presumptive GOP nominee.
The move comes as Trump faces continued deep resistance from many quarters of his party conceed by his contentious statements.
Aside from the controversies that have hung over the Trump campaign in recent weeks – including his Idea claiming a judge is biased against him in the Trump University case because of his Mexican heritage; his renewed calls for a Muslim immigration ban; and his decision to revoke credentials for The Washington Post – the campaign is also entering a new and arguably tougher phase as Democratic groups start spending big against him.
Hillary Clinton and her Democratic allies have invested at least $41 million in commercials in crucial states such as Ohio, Florida and Nevada over the next six weeks. Those messages will be echoed by hundreds of Clinton workers in those same states and amplified by President Obama and other top Democrats.
Vice President Biden is also delivering an anti-Trump speech Monday.
FoxNews.com's Christopher Snyder and The Associated Press contributed to this report.