When Jessica was with Nick, they did USO tour(s) and were considered Republicans (not sure if both are or not).
Jessica Simpson sang for the Bush inaugural celebration and is Republican from everything I have seen.
"Still, he said of the president, “We are huge fans of him and of his family, his girls. Jessica loves the heck out of him.” http://www.msnbc.msn.com/id/11849399/
He chose Jessica on purpose.