A white feather is a symbol of cowardice. So, in context, perhaps the heart symbolizes courage.
I never knew this value existed for a white feather.
As I said in the thread- the artist likely explains the symbolism of this work.
After all, there are several other objects to consider, such as the Capitol Bldg., in the background, the money and rifles, etc., and where they are placed and by whom they reside.
Also, should we compare the placement of U S Presidents in the image at the table, to the original apostles (juxtaposed against these) modern positions of surrogates?