Investors bracing for Elon Musk to sell off a chunk of his Tesla shares drove the stock down Monday morning.

The selloff came after Musk put up a poll on Twitter asking users whether he should offload a tenth of his shares.

Users voted yes by a margin of 58% to 42%, with more than 3.5 million votes cast.

Tesla shares were down 4.5% to $1,167.52 in pre-market trading Monday.

"I will abide by the results of this poll, whichever way it goes," Musk said on Twitter when he started the poll Saturday.

After the results came in, he pledged to follow through.

"I was prepared to accept either outcome," he wrote.

The move comes after Musk expressed discontent with a proposal by Democrats on Capitol Hill to impose an extra tax on the wealth of billionaires to pay for social programs. The tax has not been approved.

End world hunger?: Elon Musk says he'll sell Tesla stock to solve world hunger if UN shows how money is spent

Twitter poll: Elon Musk should sell 10% of his Tesla stock

He has other reasons to sell shares, too.

Musk has "a big tax bill coming due from his 23 million stock options awarded in 2012 that have vested and expire in August 2022 and he was going to sell some stock before year-end," Wedbush Securities stock analyst Dan Ives said in a research note.

Musk owns about 23% of Tesla. If he follows through on his pledge to sell a tenth of his shares, he would still own more than 20% of the company, a stake worth nearly a quarter of a trillion dollars.

"Note, I do not take a cash salary or bonus from anywhere," Musk said on Twitter. "I only have stock, thus the only way for me to pay taxes personally is to sell stock."

Investors had expected Musk to sell 5% to 6% of his shares to cover his coming tax bill, Ives said.

The decision to sell 10% "could surprise some investors but ultimately it's a digestible number we are not overly concerned about," Ives said. "We would rather Musk rip the Band-Aid off now and sell this portion of stock rather than it lingering over the next year and feeding into any non-fundamental bear thesis on the story."

Musk also recently raised the possibility that he would sell $6 billion in Tesla stock to help end world hunger – but only if the United Nations could transparently prove that it would work.