The Washington Post (NYSE:WPO) reported Monday that the Arizona senator has championed some "green" causes while

casting sometimes contradictory votes on other environmental bills.

The newspaper said McCain has supported a federal limit on greenhouse gas emissions, but has voted against increasing fuel-efficiency standards and resisting efforts to require utilities to offer a specific amount of electricity from renewable sources.

Doug Holtz-Eakin, McCain's senior policy adviser, said the senator does not always please "environmental groups who are single-issue, litmus test" organizations.

When compared to his Democratic rivals Sens. Hillary Clinton of New York and Barack Obama of Illinois, McCain scores significantly lower than they do in interest groups' studies.

McCain's lifetime League of Conservation Voters score is 24 percent, compared with 86 for Obama and 86 for Clinton; Defenders of Wildlife Action Fund's conservation report card gave him 38 percent in the 108th Congress and 40 in the 109th.