What A Kennedy-Markey Showdown Means For Massachusetts

Congressman Joe Kennedy III will challenge incumbent Sen. Ed Markey in next year's Democratic primary.

Sources close to Rep. Kennedy say he'll officially announce his campaign on Saturday in East Boston, where the Newton Democrat's great-great-great grandparents settled when they immigrated from Ireland in 1849.

Markey was already facing two primary opponents, but Kennedy's decision to run pits two political powerhouses against each other.

Kimberly Atkins, WBUR senior news correspondent. She tweets @kimberlyeatkins.