Chelsea Clinton and her husband, Marc Mezvinsky, are in contract to buy a $10.5 million apartment in The Whitman, at 21 East 26th St. Come June, NoMad residents will be keeping up with the Clintons. Chelsea Clinton and her husband, Marc Mezvinsky, are buying a sleek, $10.5 million apartment overlooking Madison Square Park, sources said. The Whitman, first built in 1924, is near the couple's current place, a rented loft in Gramercy Park. The 5,000-square-foot pad, in The Whitman at 21 E. 26th St., is just a few blocks from the couple's rented Gramercy Park loft. Sources said staying nearby...