>> reporter: there was a shadow over president clinton's official portrait, no, not his. look closely. there on the left of the frame, beneath the mantle, look familiar? that according to the artist is the shadow of then intern and presidential mistress monica lewinsky, wearing the infamous blue dress that nearly brought down the clinton marriage and presidency. the national portrait gallery actually has ten formal portraits of president clinton. it can rotate through its display. by coincidence, the museum says the portrait with the unwelcomed intruder is in storage. artist nelson shanks told the "philadelphia daily news" that while painting he could never get this monica thing completely out of his mind. and he confirmed to abc news he deliberately inserted lewinsky to remind close observers of the scandal and the shadow it cast. no comment from the clintons, but the gallery says no one has asked it be removed from the