McCain's support for climate change measures like a cap-and-trade system differs with a more conservative, hands-off approach backed by President Bush and other Republican leaders, the Politico reported Tuesday. The expected Senate debate may well divide the party publicly, with Democrats not expected to offer any bipartisan compromise proposals to give McCain political cover before a key procedural vote scheduled for June 2.

Behind-the-scenes coordination efforts continue with Senate Minority Leader Mitch McConnell, R-Ky., with weekly meetings. But many Republicans remain uneasy with McCain's support of government-mandated carbon emission reductions, the Politico said.

McCain's earlier and stronger stands on fighting global warming may have benefits, however, observers suggested to the Politico. Republican conservatives are looking for legislative options rather than simply playing defense against environmentalists. It may actually be good for McCain to show some independence from his party and Bush, said McCain campaign spokesman Tucker.