Sen. John Kerry starts campaigning for Senate hopeful Elizabeth Warren

By Glen Johnson, Globe Staff

Senator John Kerry today begins the delicate task of campaigning for Senator Scott Brown’s political opponent while not alienating himself from his junior colleague.

The Massachusetts Democrat will attend a morning campaign event in Somerville and an evening fund-raiser in Boston for Elizabeth Warren, the Harvard Law School professor challenging Brown for reelection.

In between, Kerry and Warren will speak at a labor rally alongside AFL-CIO President Richard Trumka.

Kerry previewed this political challenge earlier this month when he hinted he would be endorsing Warren soon. He avoided a question about whether Brown’s political record — which has led the Republican to be ranked by one publication as the second-most bipartisan member of their chamber — offered just the kind of political compromise the senator says is needed in American politics.

“What I want to do is first explain why I’m supporting Elizabeth, and I will do that somewhere in the next few days, and then we will go into the differentials and other pieces of it,” Kerry told reporters after he addressed the Massachusetts delegation to the Democratic National Convention.

Earlier, in his remarks to the delegates, Kerry said Warren was right to focus the night before on their party’s effort to promote the middle class, over what he labeled as the Republicans’ concern for the needs of the top 1 percent of income earners.

“We have an opportunity to elect an outstanding US senator who can be part of the team,” Kerry said. “I want to stay as chairman of the (Senate Foreign Relations) committee, not back to ranking member. I want Harry Reid there, ready to fight as majority leader. We need Elizabeth Warren.”

A Brown spokeswoman said that the election “isn’t about if Senator Kerry and Senator Reid get to keep their jobs. It’s about if the people of Massachusetts get to keep theirs.”