Charles Haldeman, who stepped down Tuesday as an executive at Boston mutual fund company Putnam, is the prime candidate for CEO of Freddie Mac ( FRE), the Wall Street Journal reports, citing people familiar with the situation. Haldeman's expected appointment is subject to approval by the Federal Housing Finance Agency, which regulates Freddie and its main rival, Fannie Mae ( FNM), and by the U.S. Treasury, the Journal reports. If Haldeman's appointment is confirmed at the government-backed mortgage company, he would succeed John Koskinen, who has served as interim CEO since March when David Moffett abruptly resigned. Freddie Mac's board was impressed by Haldeman's efforts to restore compliance systems at Putnam after regulators accused the company of inappropriate trading over several years starting in 1998, the Washington Post reports, citing a source. Both Fannie and Freddie were seized by the U.S. government in September as the mortgage crisis in the U.S. deepened.