Shadowy surprise in painting of former president

A portrait of former President Bill Clinton is sparking controversy. Renowned painter Nelson Shanks said he included a shadow of Monica Lewinsky's infamous blue dress.

Shanks said it was his goal to paint an important part of his subject's history, and in this case, that history led to Shanks to place a hidden message within his depiction of the 42nd president, reports CBS News White House correspondent Bill Plante.

"My job is to look into their soul and they to allow me to do so," Shanks said.

For six decades, Shanks has had an eye and a brush on history. The 77-year-old has painted princesses and popes, but when it came to recording Clinton's presidency for the canvas, Shanks said he added a little something extra -- a shadow of Lewinsky's blue dress.

"The shadow represented a way of breaking the horizontal line of the mantelpiece," he said.

After spending nearly 20 hours with Clinton, Shanks continued his work at home with a mannequin and he soon realized something was missing.

"I was rifling through the closet to get something to throw over the mannequin to complete the shadow shape and it just happened to be a blue dress," Shanks said.

He said including Lewinsky's dress from the Gap brought a more practical function to his art.

"The shadow itself not only functions as a block in the composition at a certain point but also as symbolism, a shadow across the administration," Shanks said.

The Clintons, however, had no idea the scandal was a part of the painting.

"Almost no one knew," he said.

News of the affair between Clinton and the White House intern broke in 1998.

Eight years later, in 2006, the portrait was revealed.

"I think you did a marvelous job, Nelson and I thank you very, very much for what you did," Clinton said at the unveiling.

Despite that warm reception, Shanks thinks this political statement has put his masterpiece in the dark.

"It's been buried," he said.

He said the portrait hasn't been displayed for several years.

The National Portrait Gallery told CBS News: "The Clintons have not asked to have the portrait removed. This is the first the museum has heard of the symbolism in the shadow."

But Shanks disagrees. He said the portrait has been "blackballed."

"What is all the fuss about? This is a great painting," Shanks said.

While the National Portrait Gallery said the portrait remains in rotation, it's not the first time it's generated controversy -- Shanks also left Clinton's wedding ring out of the painting. CBS News reached out to former President Clinton and Lewinsky and did not receive comment.