The Democratic field continues to thin in Massachusetts' U.S. Senate race.
Newton engineer Herb Robinson is the latest candidate to drop out, making the announcement Thursday.
He says he originally intended to run for the 4th Congressional District seat, currently held by Rep. Barney Frank.
"Now that Barney has retired and Elizabeth Warren has pretty much taken over the Senate race, I switched back to the original plan," Robinson said.
Apart from Warren, the front-runner, two other Democrats are still vying to run against Republican Sen. Scott Brown next year — attorneys Marisa DeFranco and Jim King.
This program aired on December 15, 2011. The audio for this program is not available.