Reuters: Two veteran U.S. senators faced potential career-ending challenges on Tuesday, as voters cast ballots in four state primary contests amid widespread anti-Washington anger ahead of November's midterm elections. Democrats Arlen Specter of Pennsylvania and Blanche Lincoln of Arkansas faced strong tests from the left, while a U.S. Senate race in Kentucky between a Republican establishment favorite and a conservative "Tea Party" activist tested the strength of that loosely organized conservative movement.