Donald Trump will try to close the fundraising gap after he debates Hillary Clinton. | Getty Trump plans post-debate fundraising blitz

Donald Trump is planning a "national call day" to Republican donors who've yet to open their wallets, hoping to close a massive fundraising gap between him and Hillary Clinton.

Trump is summoning his top fundraisers to Trump Tower on Tuesday, the day after he squares off with Hillary Clinton in the first presidential debate. The fundraisers are being asked to "prepare call lists of prospective donors" and to recruit at least three people from their home states to raise funds on Tuesday, according to a copy of the invitation.


Two people briefed on the event said it would be geared toward attracting the support of Republican contributors who have yet to commit to Trump financially. Many of the party's top donors have expressed profound reservations over Trump's candidacy and have chosen to direct their funds to down-ballot races.

The push comes amid mounting concern that Trump, who has lagged in the fundraising race, is being outspent and out-organized in the states that will determine the election. Hillary Clinton has outspent Trump on the TV airwaves by a stunning 7-to-1 margin and in many battlegrounds has dozens more offices and field staffers than the Republican nominee.

Through the end of August, Clinton has outraised Trump $373 million to $165 million.

Among those still on the sidelines are many of the GOP's biggest donors. Trump suffered a blow this week when Las Vegas casino mogul Sheldon Adelson revealed that he would be directing $40 million to Republican groups devoted to protecting the party's congressional majorities and just $5 million toward electing the GOP presidential nominee. Adelson had once been seen as a potential major Trump donor and seen as possibly giving as much as $100 million to boost his candidacy.

Tuesday's event will be hosted by vice presidential nominee Mike Pence and two of Trump's children, Eric and Ivanka. It is being co-chaired by Republican fundraisers Anthony Scaramucci, a prominent Wall Street investor, and Roy Bailey, a Dallas insurance executive. Bailey has long been close with former New York City Mayor Rudy Giuliani, a prominent Trump surrogate and adviser.

In the invitation, the campaign says it will offer four invitations to next week's presidential debate to fundraisers who pull in at least $250,000 by Friday.