Democrat Elizabeth Warren holds a slim lead in her battle against Republican Scott Brown for US Senate in Massachusetts, a Democratic polling company has found. The new poll released today by Public Policy Polling found Warren leading Brown, 46 percent to 41 percent. The poll had a margin of error of plus or minus 3.2 percentage points. The poll found Brown would win 89 percent of Republican voters, 17 percent of Democrat voters, but only 48 percent of independents, a far cry from the 64 percent he won in his January 2010 special election race with Democratic Attorney General Martha Coakley.