(CNN) - Arkansas Sen. Blanche Lincoln won the Democratic primary Tuesday night, beating back a challenge from Lt. Gov. Bill Halter in this high profile contest that exposed a rift between the liberal and centrist wings of the Democratic Party.
Lincoln was targeted by national unions and liberal activists, who accused the Arkansas Democrat of turning her back on them as well as failing to support President Obama's policy goals.
The Lincoln critics found their candidate in Halter and poured millions of dollars into Arkansas. Halter officially announced his candidacy in March making the primary a sprint, not a marathon.
With the help of these outside activists, the lieutenant governor forced Lincoln into this June runoff election after she failed to receive more than 50 percent of the vote in last month's primary.