Bill Ackman once called Pershing Square’s investment in Fannie Mae and Freddie Mac, the two mortgage giants that have been in the federal government’s hands ever since the financial crisis, “a lottery ticket in the drawer, but one that’s enormously profitable. “

Could this be the year that Ackman cashes that lottery ticket, which according to some estimates could be worth as much as $10 billion? For perspective, that would be half the size of his entire hedge fund enterprise.

Ackman is known for contrarian bets that can sometimes be big winners. These particular stocks are soaring at a time when the Trump administration has acknowledged it plans to sell a portion of the two government sponsored enterprises in the public markets.

They are also boosting the hedge fund in a volatile market. Pershing Square’s publicly traded hedge fund is up 18.4 percent net at the end of August compared with the broader market’s gain of 10.5 percent, and Fannie and Freddie accounted for almost half of those gains.

Over the past year, Fannie’s shares have risen almost a thousand percent and they’re up almost 300 percent this year alone. As a result, Fannie Mae has become Pershing Square’s most profitable holding of the year, and Freddie Mac is third.

According to a report to investors on August 19th, Fannie shares provided 6.1 gross percentage points of the fund’s gross gain of more than 22 percent this year, while Freddie Mac accounted for 4.3 percentage points. Together, that comes to a total of 10.4 percentage points of the total gross performance.

Recently, Bill Pulte, who heads the Federal Housing Finance Agency that oversees Fannie and Freddie, said the U.S. government was looking to sell around 5 percent of the two mortgage finances in a public offering. He also said he thought those two companies were worth between $500 billion and $700 billion to the U.S. government, which owns 80 percent of the shares. The rest is owned by investors and traded in the OTC market.

Ackman has been more conservative in his valuation, pegging the GSEs’ worth at $300 million. The size of Pershing Square’s stake is unknown because it quit reporting that to the Securities Exchange Commission several years ago. But when Ackman first invested in Fannie and Freddie in November of 2013, the hedge fund owned about 10 percent of the 20 percent of the GSEs that the government does not own, which would give it a .02 percent stake in the enterprises. Under Pulte’s valuation, that would be worth around $10 billion — or more.

Fannie Mae is now trading around $12 a share compared to the single digits of recent years. When Ackman bought it in November 2013, it traded between $2 and $3 per share. It has long been a drag on the fund’s performance.

Years ago, unsuccessful attempts to wrest the GSEs from government control led the two giants to become known as widow makers at prominent hedge funds. Perry Capital and Paulson and Co. lost a lot of money betting on the mortgage giants’ privatization.

After Ackman’s endorsement of President Trump last summer, he told investors that the privatization of Fannie and Freddie would be “the biggest deal of all times, and I think it’s one President Trump would like to be the one to negotiate and we’ll be delighted to help him if we can.”

Ackman has spoken about the possibility of the privatization of Fannie and Freddie under Trump several times over the past few years, but this is the closest his hopes have ever come to being realized.

A Pershing Square spokesman declined to comment.