CHICAGO, Aug 20 (Reuters) - After Kamala Harris secured the Democratic presidential nomination in an unprecedented party upheaval, she got some advice from former President Barack Obama: Tap the campaign talent pool that is out there; you can have anyone you want. Within days, Obama's former campaign manager David Plouffe and other high profile alumni from Obama's 2008 and 2012 election efforts joined her nascent campaign. "He just wanted her to know that she was in a position to recruit anyone she thought they needed," said a source familiar with Obama's and Harris' conversation.