Arkansas Lt. Gov. Bill Halter and former Arizona Rep. J.D. Hayworth are mounting two of the country's highest-profile primary challenges to incumbent senators, and both showed this week that their efforts can't be dismissed. Halter reported raising $2 million since announcing his campaign against Democratic Sen. Blanche Lincoln on March 1. Hayworth's camp, meanwhile, says it brought in over a million dollars for the first quarter to fund the ex-congressman's challenge to Sen. John McCain.

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