On the heels of blasting John McCain's selection of Alaska Gov. Sarah Palin as his running mate, Lindsay Lohan reportedly got a bit of a jolt from an unexpected quarter: the Obama-Biden campaign. Apparently, LiLo was interested in becoming very involved in the Democratic ticket's bid for the White House -- even offering to host a series of events appealing to younger voters. However, a top source in the Barack Obama team tells me the actress ''is not exactly the kind of high-profile star who would be a positive for us.''Given Lohan's past problems, plus ongoing brushes with controversy, I've learned the campaign quietly told the actress ''thanks, but no thanks,'' but in far more diplomatic terms.