Democratic presidential candidate Andrew Yang teased that he would do something unprecedented during Thursday's debate, and he did — he announced he's offering $1,000 to 10 random families for a year. The idea reflects his proposal to give every American adult $1,000 a month, which he calls the "Freedom Dividend."

But debate watchers quickly raised the question of whether it's legal for a presidential candidate to give money to potential voters. Yang has offered money out of his own pocket before as a way to prove his plan would make people's lives better, but this money would come from his campaign coffers.

When CBS News' Ed O'Keefe asked Yang after the debate if he checked that with an election lawyer, Yang responded "Oh yeah, of course. We have this whole army of lawyers who signed off on it. But I want everyone to reflect for a moment that we live in a world where a billionaire can spend over $10 million buying his way onto the election stage and everyone thinks that is totally appropriate. But then I'm literally giving money to Americans around the country to do whatever they'd like to help improve their lives, and that seems problematic."

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Deborah Hellman, a law professor at the University of Virginia School of Law who has written about campaign finance law, said she doesn't think the offer is illegal, because it doesn't implicitly or explicitly ask for anything in return.

"I would think that Yang's proposal is not illegal as he isn't suggesting that he will give money to voters in exchange for their votes, either explicitly or implicitly," Hellman said. "Why the proposal may seem problematic is that we may worry that the voters will feel grateful to Yang and vote for him for that reason."

But the Supreme Court, she noted, has been clear that ingratiation isn't corruption.

"In my view, we should worry more about the debt of gratitude that elected officials may feel to wealthy individuals who either make large contributions to their campaigns or who expend large sums in support of their campaigns," Hellman added.

Campaign finance expert Rick Hasen, who teaches campaign finance at the University of California's Irvine School of Law, also tweeted Thursday night that Yang's tactic doesn't appear to violate campaign finance laws.

"I don't see a legal problem so long as it is not tied to voting or registering," Hasen tweeted, adding, "I don't see it as personal use for the candidate. It is a form of campaign advertising."

Yang, an entrepreneur, says his plan to offer a universal basic income would allow people to pursue careers and take care of families without fear of putting food on the table. It's become the central plank of his unusual candidacy, which is doing well enough to get him to the debate state on Thursday.

Yang's approach has, for someone who was virtually unknown before running for president, paid off. Yang spoke for the least amount of time on stage Thursday night, but was the top trend on Twitter during the debate.