President Trump wants to privatize Fannie Mae and Freddie Mac. A survey shows nearly half of investors expect it by 2028.

Billionaire Bill Ackman helped fund the spinoff of Howard Hughes Holdings Inc. from General Growth Properties in 2010 and has been a big shareholder in the real-estate company since then.

In the wake of widespread regulatory reform after the 2008 financial crisis, the federal government placed Fannie Mae and ...