Throughout the summer of 2008, Obama typically led McCain in national polls by single-digit margins, and also led in several key swing states. McCain reprised his familiar underdog role, which was due at least in part to the overall challenges Republicans faced in the election year. McCain accepted public financing for the general election campaign, and the restrictions that go with it, while criticizing his Democratic opponent for becoming the first major party candidate to opt out of such financing for the general election since the system was implemented in 1976. The Republican's broad campaign theme focused on his experience and ability to lead, compared to Obama's.