(CNN) Stephen Schwarzman, an informal adviser and donor to President Donald Trump, is hosting a fundraiser with Sen. Mitt Romney in support of several Republicans colleagues seeking reelection, according to two people with knowledge of the event.

The event, which is intended for a small group of influential donors at Schwarzman's Park Avenue apartment, is scheduled for Thursday, said one of the people.

A spokeswoman for Romney confirmed the event.

Helping Romney bolster his standing in the party as he attempts to cement his position as a self-described "renegade Republican" during an impeachment inquiry is notable because of Schwarzman's support for Trump. Since the 2016 election, Schwarzman has donated a total of about $850,000 to Trump's inauguration and political action committees, based on records compiled by CNN and the Center for Responsive Politics.

The event provides donors a chance to gauge how far Romney may go in possibly building support for a GOP coalition against Trump. Romney recently ratcheted up his attacks on Trump following a series of decisions by the President. Like other members of his party, Romney blasted Trump for abandoning the Kurds in Northern Syria. He was also one of the loudest voices rebuking the President for urging Ukraine and China to investigate Vice President Joe Biden's family

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