President Donald Trump has billed his July Fourth rally on the National Mall as a culmination of the “most unforgettable birthday party any country has ever seen.” But inside his White House, there’s growing angst over how many people will actually show up to celebrate.

The lackluster attendance for Trump’s speech on the mall last week — a fact that has infuriated the president behind the scenes — has sparked fears of a similarly disappointing turnout when he headlines an Independence Day celebration, sources familiar with the matter told CNN. He has teased the event as one of the most consequential moments of his presidency.

The high-profile address follows days of scattered crowds and setbacks at the “Great American State Fair” that’s taken over the iconic two-mile stretch of downtown Washington, DC. And with tightened security measures, triple-digit heat and a schedule set to run well into Saturday night, White House officials are already bracing for an underwhelming showing.

“I do not understand why we are doing this so late,” one White House official vented, noting there were still ongoing efforts to fix the timing. “I’m really not sure who thought this was a good idea.”