Republican Scott Brown has surged to a double-digit lead over Democratic rival Martha Coakley in three Bay State communities identified as bellwethers, according to the latest Suffolk University bellwether polling of the race for U.S. Senate heading into tomorrow’s Massachusetts special election.

Gardner, Fitchburg and Peabody all show solid margins for Brown, the state senator running against Attorney General Coakley. Those cities were identified as bellwether communities because in the most recent “like election” – the November 2006 Senate race between the late Sen. Edward M. Kennedy and Republican challenger Kenneth Chase – the results in all three communities were within 1 percentage point of the actual statewide results for each candidate. Additionally, party registration in those cities is similar to the statewide voter makeup.

“Brown has continued to build on the momentum that we saw last week in the Suffolk University statewide poll,” said David Paleologos, director of the Suffolk University Political Research Center in Boston. “There’s still a day left, and a number of factors, including weather, can affect turnout, but the latest bellwether polls suggest a solid lead for Brown.”

Suffolk University released a statewide poll Thursday, Jan. 14, that showed Brown (50 percent) leading Coakley (46 percent) by 4 points. The results showed a race within a margin of error of 4.38.

The bellwether polling, conducted Saturday, Jan. 16, and Sunday, Jan. 17, shows:

  • Brown (55 percent) leads Coakley (40 percent) by 15 points in Gardner. Independent candidate Joseph L. Kennedy polls 2 percent, while 3 percent are undecided.
  • In Fitchburg, Brown (55 percent) has a 14-point lead over Coakley (41 percent), with 2 percent for Kennedy and 2 percent undecided.
  • Peabody voters give Brown (57 percent), a 17-point lead over Coakley (40 percent), with Kennedy polling 1 percent and 3 percent undecided.

The bellwether polls are designed to predict outcomes and not margins. Suffolk’s bellwether polls have been 96 percent accurate in picking straight-up winners when taken within three days of an election since 2006.

Results of the November 2006 survey in the three bellwether communities closely traced the final statewide outcome. Those 2006 results were as follows:

  • Statewide: Edward M. Kennedy (D), 67 percent; Kenneth Chase (R), 29 percent; blanks, 4 percent
  • Gardner: Kennedy, 68 percent; Chase, 30 percent; blanks, 3 percent
  • Fitchburg: Kennedy, 67 percent; Chase, 30 percent; blanks, 4 percent
  • Peabody: Kennedy, 67 percent; Chase, 29 percent; blanks, 4 percent

Party registration in the three bellwether communities largely mirrors statewide registration, with the following breakdown:

  • Massachusetts statewide: Democrats, 36 percent; Republicans, 12 percent; unenrolled, 52 percent
  • Gardner: Democrats, 35 percent; Republicans, 12 percent; unenrolled, 53 percent
  • Fitchburg: Democrats, 34 percent; Republicans, 11 percent; unenrolled, 55 percent
  • Peabody: Democrats, 35 percent; Republicans, 9 percent; unenrolled, 56 percent