More traders on the online political stock market PredictIt are doubting whether President Donald Trump can remain in office through the end of 2018.

As accusations and intense scrutiny over various facets of the Republican's leadership continue, the market has said Trump's odds of remaining in power are diminishing, PredictIt co-founder John Aristotle Phillips told CNBC on Friday. "It's almost 50-50 that he won't be in office by the end of 2018."

PredictIt data shows that the probability of Trump still leading the country in 2019 stood between 60-70 percent from February to early May. The market hit a high of 75 percent on May 8, the day former acting attorney general Sally Q. Yates testified about Russian interference in the 2016 presidential election.

A chart depicting the PredictIt market for the question "Will Donald Trump be president at year-end 2018?"

But since then, odds have steadily dropped and hit a low of 53 percent on May 17. That was the day the Dow lost nearly 2 percent on news of a memo by former FBI Director James Comey that detailed how Trump urged him to stand down on an investigation into fired national security advisor Michael Flynn.

More than 320,000 shares have traded on the market.

Trump's recent series of scandals have sparked debate on his presidency's survival, but despite talk of potential impeachment, only 20 percent of PredictIt players anticipate that scenario in 2017, Phillips said. Nomura mirrored those sentiments in a Thursday report, stating that impeachment "still seems a distant prospect."

A chart depicting the PredictIt market for the question "Will Donald Trump be impeached in 2017?"

A futures market for politics, PredictIt allows participants to bet on the outcomes of future political events across the world. Each event is phrased as a question and traders can buy shares on the listed outcomes, each of which have a probability between 1 to 99 percent. PredictIt, a project of New Zealand's Victoria University of Wellington, converts those probabilities into U.S. cents.

"If the market is pricing the odds of Trump's impeachment at 20 cents on the dollar and I think that is too low, I would buy shares," explained Phillips. "If the price rises to 30 cents and I feel this is an overestimate, I can sell my shares for a 10 cent profit. The price of the share at any moment in time fluctuates, according to the market's expectations."

Aside from Trump-related events, the other biggest movers on Friday included contracts on the new Senate-confirmed FBI director, the next leader of Ireland's Fine Gael and the next U.K. party leader to leave.

Phillips said he believes prediction markets such as PredictIt are "things of the future," noting they typically offer better insights than traditional polls.

"When people answer a poll, they say what they want to have happen, who they're going to vote for, etc. When it's a market, people are putting money where their mouth is. They're not talking about what they want to have happen, they're talking about what they think will happen."