Donald TrumpDonald John TrumpMilitary personnel to handle coronavirus patients at facilities in NYC, New Orleans and Dallas Navy hospital ship USNS Comfort has total of 20 patients: report Fauci says that all states should have stay-at-home orders MORE campaign spokeswoman Katrina Pierson said Thursday she thinks half of all Bernie SandersBernie SandersHuffPost political reporter on why Bernie fell way behind Biden Schumer: Administration 'must move heaven and earth' to implement new unemployment benefits Biden associates reach out to Holder about VP search MORE supporters will vote for the presumptive Republican presidential nominee in November. 

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"I think it's probably going to be half at some point," Pierson said on CNN.

"Younger voters want to see the status quo busted up, and for those voters — those are going to be trigger voters. They're not really concerned about all the other things, and it really transcends party, and right now in a race between Hillary ClintonHillary Diane Rodham ClintonFormer Obama adviser Plouffe predicts 'historical level' of turnout by Trump supporters Poll: More Republican voters think party is more united than Democratic voters Whoopi Goldberg presses Sanders: 'Why are you still in the race?' MORE and Donald Trump, Donald Trump is the only option to break up that system." 

Trump made his case to Sanders supporters after Clinton became the Democratic Party's presumptive nominee this week, saying he "welcomes them with open arms." 

"To all of those Bernie Sanders voters who have been left out in the cold by a rigged system of superdelegates, we welcome you with open arms," Trump said Tuesday. 

But Clinton has said she hopes — and expects — Sanders supporters to unite behind her to defeat Trump in the general election. And he said Thursday, in a statement following a meeting with President Obama at the White House, that he would work with her to defeat Trump

Some lawmakers supporting Sanders have called on the Vermont senator to rethink his campaign and unite with Clinton now, instead of waiting for votes to be cast in next week's primary in Washington D.C.

White House press secretary Josh Earnest, however, noted it’s up Sanders to decide when and how he ends his campaign, though that message came shortly after President Obama formally endorsed Clinton, a move that is likely to suck the remaining energy from the Vermont senator’s campaign.