USA TODAY's Melina Khan breaks down multiple outcomes of the ongoing government shutdown.

It's the first day of the U.S. government partial shutdown, but how long will it last? A few days? A few weeks? While only Capitol Hill and the White House can answer that question, that's not stopping people from placing bets on future events.

Polymarket and Kalshi have opened markets on the duration of the standoff, with users anticipating a long-term shutdown of the federal government.

While the Republicans control both the House of Representatives and the Senate, they need at least seven Democratic votes to pass any spending bill out of the Senate, where 60 votes are required to advance most legislation in the 100-seat chamber.

Democrats are using that leverage to push for the continuation and expansion of tax breaks for about 24 million Americans who buy insurance through the Affordable Care Act. So far, they have refused to back a government spending bill that does not address the issue.Republicans say they are open to considering a fix for the expiring ACA tax breaks, but will only support a simple stopgap spending bill that would fund the government through Nov. 21. This legislation does not include any changes to ACA subsidies.

When does Polymarket think the government will reopen?

Polymarket activity suggests users expect the shutdown to continue until at least mid-October or later.

The site gives a 35% likelihood for the shutdown lasting 15 days or longer, with over $200,000 in volume put on an extended government closure.

The prediction market gives the same odds for the shutdown lasting between roughly one and two weeks. The market for a government reopening between Oct. 6 and Oct. 9, as well as the market for a reopening between Oct. 10 and Oct. 14, both show a 28% chance.

The site gives a reopening date between Oct. 3 and Oct. 5 a 7% chance and a return before Oct. 2 a less 1% chance.

When does Kalshi think the government will reopen?

Kalshi action indicates that users think the shutdown is likely to last at least four days and possibly more than 10 days.

The site gives an 89% chance of the shutdown lasting "more than 4 days," an 87% probability of lasting "more than 5 days," and a 54% likelihood of lasting "more than 10 days." However, the odds for a shutdown "lasting more than 15 days" dip to 33%.

Near-term closure appears to be a certainty for Kalshi users, with shutdown durations shorter than three days all having better than 90% odds.

What are prediction markets?

Prediction markets like Polymarket and Kalshi offer "event contracts" that allow trading on the outcomes of various events, including politics, sports and natural disasters. Each contract has a yes-or-no option that pays $1 to the winning side.

The contracts are traded on a market similar to commodity futures, according to Brian Flaherty of the Alts.co newsletter.

"In sportsbooks and casinos, you're betting directly against the platform," Flaherty wrote. "Event contracts, however, are a form of peer-to-peer betting in which you trade directly against other bettors."

Flaherty warns that contract prices "approximately reflect collective beliefs" but do not reflect true probabilities.

Polymarket's CEO Shayne Coplan revealed in a social media post on Sept. 3 that the company had received "the green light" from the Commodity Futures Trading Commission (CFTC) to resume U.S. operations. This action follows earlier charges in 2022 for offering illegal event-based options, as reported by The Street.

The pseudo-gambling format was skewered on the "Conflict of Interest" episode of "South Park." Jeff Edelstein, a columnist for gambling news outlet In Game, said the episode "cuts to the heart of ongoing debates about where we draw the line."

"Should you be able to bet on war? Natural disasters? Personal tragedies? These aren't just abstract questions anymore," he wrote.

Contributing: Joey Garrison - USA TODAY; Reuters

When will the government shutdown end? Here's what the prediction markets think