From the Associated PressIndiana's embattled Secretary of State Charlie White is advising presidential campaigns to be careful following revelations of questionable signatures on petitions in the 2008 contest. White said Friday he will be looking for organized efforts to fraudulently place a candidate on the ballot. He also recommended candidates looking to run in Indiana's May 2012 primary begin organizing early. The South Bend Tribune and Howey Politics Indiana reported this week that they found hundreds of questionable signaures on petitions used for Democratic presidential candidates Hillary Clinton and Barack Obama. Indiana Republican Party Chairman Eric Holcomb has requested a federal investigation. Democratic Party Chairman Dan Parker said Friday he would support a probe. White is facing trial in January on charges he voted illegally in the 2010 election.