McCain began 2001 by breaking with the new George W. Bush administration on a number of matters, including HMO reform, climate change, and gun control legislation; McCain–Feingold was opposed by Bush as well. In May 2001, McCain was one of only two Senate Republicans to vote against the Bush tax cuts. Besides the differences with Bush on ideological grounds, there was considerable antagonism between the two remaining from the previous year's campaign. Later, when a Republican senator, Jim Jeffords, became an Independent, thereby throwing control of the Senate to the Democrats, McCain defended Jeffords against "self-appointed enforcers of party loyalty". Indeed, there was speculation at the time, and in years since, about McCain himself leaving the Republican Party, but McCain had always adamantly denied that he ever considered doing so. Beginning in 2001, McCain used political capital gained from his presidential run, as well as improved legislative skills and relationships with other members, to become one of the Senate's most influential members.