Tammy, Shelley, Heidi, Mazie, and Elizabeth: a lineup of women that Democrats say is their best hope of keeping control of the U.S. Senate. All are in competitive races, and with Republicans needing to pick up just four seats to take control, the balance of power could come down to these five: Tammy Baldwin in Wisconsin, Shelley Berkley in Nevada, Heidi Heitkamp in North Dakota, Mazie Hirono in Hawaii, and Elizabeth Warren in Massachusetts.