Matheson said the weekend votes are common for him, and he doesn't feel bound to vote with his party.

"I think people have figured out a long time ago that I vote on substance, not party," Matheson said Monday.

He split with Democrats on legislation to overhaul U.S. energy policy and approve electronic surveillance without warrants in some cases.

The surveillance bill Matheson supported - which was signed by President Bush on Sunday - gives the National Security Agency authority to conduct electronic surveillance without warrants on communications between foreign parties "reasonably believed to be outside the United States."

Democratic opponents argued the bill gave the president far too much power to monitor communications.

Matheson said he had been told in briefings that there had been "increased chatter" and, as a result, "I felt it was important we had something in place before Congress left town."

He was one of 41 Democrats to vote for the bill. Utah's Republican House members and senators also voted for the surveillance legislation.

Karen McCreary, executive director of the Utah chapter of the American Civil Liberties Union, said Matheson's vote and Congress' quick approval of the surveillance is troubling. Those that voted for the bill, she said, are "caving in at a time where it is really critical that we have Congress play its important role to protect the Constitution and be an important balance."

Matheson backed a Democratic proposal that would have set more limits on the intelligence surveillance, but that bill could not pass the Senate before Congress recessed until after Labor Day.

Matheson was also one of 11 Democrats who voted against major revisions of U.S. energy policy. He said he was concerned that provisions in the bill would impose new bureaucratic hurdles that would have reduced natural gas production and hurt consumers.

Steve Bloch, an attorney with the Southern Utah Wilderness Alliance, said the votes showed "a lack of leadership, a lack of direction for the future."

"He is clearly aligning himself with policies that haven't worked these past several years and are out of balance with what I think the majority of the country is coming to realize - that we can't be dependent on fossil fuel, that we need to move in a new direction and his direction is firmly tied to looking to the failed policies of the past," Bloch said.

Matheson also was one of 11 Democrats to vote against a tax bill aimed at expanding renewable energy production.

Both of Utah's Republican House members, Reps. Chris Cannon and Rob Bishop, voted with Matheson in each instance.

Bucking his party is not unusual for Matheson. According to a vote analysis by Congressional Quarterly, he broke ranks with party leaders in roughly one of every six votes, including being one of 10 Democrats who last month voted against a timeline for a withdrawal from Iraq.

Matthew Burbank, a political science professor at the University of Utah, said he thinks Matheson has staked out a position more conservative than most Democrats for two reasons: the conservative makeup of his district and his personal views.