Cowan sworn in as interim Massachusetts senator

Cowan, flanked by Sen. Elizabeth Warren (D-Mass.) Kerry, was sworn in by Vice President Biden. He is now the Senate's second black senator, and the only black Democratic senator.

He will serve until a special election to replace Kerry occurs in June. Democrats are likely to retain the seat, as Massachusetts Republicans have been unable to front a strong challenger since former Sen. Scott Brown (R-Mass.) decided against a run.

Reps. Edward Markey and Stephen Lynch have both announced their intentions to pursue the Democratic nomination for the seat, and face a primary on April 30.

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