WASHINGTON — Having lost his cash advantage, President Donald Trump has entered the final stretch of his re-election race facing a perfect storm of fundraising headwinds, including a base of big donors who are maxed out, choosing to sit on the sidelines or shifting their resources to increasingly competitive Senate races.

Trump raised $210 million in August — a sizable sum, but far short of Democratic nominee Joe Biden's $365 million haul. Despite the president having a nearly three-year fundraising head start on Biden, both campaigns at the end of July had nearly the same amount of money remaining in their war chests. Neither campaign has released their full financial filings for August.

Now, heading into the final weeks of the race, many major Republican donors have reached the limit on how much they can legally give. Others are hesitant to give more after seeing the campaign burn through $800 million this cycle only to trail Biden nationally and in key swing states in polls. At the same time, donors are being solicited to contribute to a growing number of Republican senators facing tough races, with several major Trump donors from 2016 pivoting their resources there.