Partisan politics threaten to derail progress on a Senate climate change bill, even before the first committee markup.

Republicans on the Senate Environment and Public Works Committee say they will carry through on threats to boycott markups on the bill, which panel Chairwoman Barbara Boxer had wanted to begin Tuesday.

The Republicans — led by Oklahoma’s James M. Inhofe , the Environment panel’s ranking GOP member and the Senate’s most vocal climate change skeptic — say they will not be present at the Tuesday session.

Because two members of the minority party must attend in order for a markup to proceed, Boxer has scheduled a “committee business meeting” — an apparent procedural gambit designed to allow work without a GOP quorum.

“The committee Republicans should rethink their approach. As long as they refuse to come to work, they are not participating in one of the most important issues facing our generation,” Boxer said in a statement Monday.

“We urge ranking member Inhofe, with the utmost respect, to bring the committee Republicans back to work on this issue. We will give them the opportunity, as we proceed this week, to reconsider their decision. We look forward to working with them if they decide to participate, but if they do not, we will move forward in accordance with the rules of the Senate and of this committee.”

The panel has a 12-7 Democratic majority and can easily approve a bill without any Republican support. But observers say the development of a partisan rift so early in the legislative process could threaten the bill’s prospects on the Senate floor, where it is unlikely to pass without some Republican support.

“It’s not the best gesture,” said Chelsea Maxwell, a partner at the Clark Group LLC, an environmental lobbying firm, and a senior climate adviser to former Sen. John W. Warner, R-Va. (1979-2009), last year’s lead Republican cosponsor of a Senate climate change bill. “It’s going to make it very difficult to convince the fence-sitting Republicans that they will be treated with respect if they come to the table,” she said.

“It’s going to hurt things,” said Robert Dillon, a spokesman for Alaska Republican Sen. Lisa Murkowski , a moderate Democrats are likely to court. “What’s needed is a serious debate and a look at all the issues. Sen. Boxer’s way of going about this is not winning any converts.”