Submitted: Apr 14, 2008 - A new survey showing Sen. Hillary Clinton leading Sen. Barack Obama by 20 percentage points in Pennsylvania comes from a polling firm with a shaky track record this election season.

The poll, which topped the Drudge Report on Monday afternoon ("shock poll"), was issued by American Research Group Inc. (ARG). In the poll, conducted on Friday, Saturday and Sunday, 57% of likely Democratic voters…