Sen. Chris Van HollenChristopher (Chris) Van HollenDem campaign chairman expresses confidence over path to Senate majority Trump draws bipartisan fire over Brennan New sanctions would hurt Russia — but hurt American industry more MORE (D-Md.) swiped at President TrumpDonald John TrumpWhite House counsel called Trump 'King Kong' behind his back: report Trump stays out of Arizona's ugly and costly GOP fight Trump claims he instructed White House counsel to cooperate with Mueller MORE on Saturday while attending the "March for Our Lives" rally in Washington, D.C., calling for action on gun violence.

Asked about estimated attendance at the rally, which was expected to draw hundreds of thousands of people, Van Hollen told The Hill, "I can tell you for sure, it's larger than the Trump inauguration."

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While exact turnout figures have yet to be released, organizers obtained a permit for 500,000 people to rally in D.C. around Pennsylvania Avenue near the White House. Hundreds of similar marches were planned worldwide.

Trump sparked backlash last year after sending then-White House spokesman Sean SpicerSean Michael SpicerSpicer slams Omarosa on WH recordings: 'She will do anything to further her own being' The Hill's 12:30 Report White House seeking to prevent Omarosa from releasing more tapes: report MORE to confront members of the media over coverage of his inauguration crowd size after taking office.

Spicer claimed the press misrepresented the number of people at the inauguration after numerous reports indicated that the crowd was much smaller than former President Obama’s 2009 inauguration crowd.

The White House spokesman claimed at the time that Trump's inauguration crowd size was “the largest audience to ever witness an inauguration, period, both in person and around the globe,” garnering pushback from the media.

Spicer said in September that he regretted his fiery exchange with reporters.

— Mike Lillis contributed