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"Obviously he just can't help himself. This is starting to look like a real campaign, and then he does this," the Republican source said. "It's awful. It's starting to look like he doesn't even want to win."
The White House referred questions about the tweet to Trump's re-election campaign.
"The President is just raising a question about the chaos Democrats have created with their insistence on all mail-in voting," said Hogan Gidley, the campaign's press secretary.
"Universal mail-in voting invites chaos and severe delays in results," stated Hogan.
Ari Fleischer, who was White House press secretary under Republican President George W. Bush, said Trump should delete the tweet.
"This is not an idea anyone, especially POTUS, should float. Our democracy is based on elections in which everyone knows the rules and they apply to all," Ari Fleischer said.
"Mr. President — please don't even pretend to mess with this. It's a harmful idea," continued Ari.
Polls have shown that US registered voters oppose an election delay.
When Reuters/Ipsos in April asked voters if they thought the election should be rescheduled due to the coronavirus, 59 percent opposed the idea, including a majority in each party.
A Joe Biden campaign official called Trump's tweet an obvious ploy to distract from the awful GDP numbers.
"We're going to keep our eye on the ball," the Biden campaign official said.
Dale Ho, director of the American Civil Liberties Union's voting rights project, said Trump lacked the authority to reschedule an election.
"This is America," Ho said. "We are a democracy, not a dictatorship. The Constitution sets the date for the election in November. Nothing President Donald Trump says, does, or tweets can change that fact."
(Writer: Steve Holland | Editors: Jonathan Oatis, Rosalba O'Brien)
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