DENVER — As Democrats prepare to launch their national convention here, a poll conducted for The Denver Post shows Democratic presidential candidate Barack Obama trailing Republican John McCain in New Mexico 45 percent to 41 percent.

The poll, which is based on interviews with 400 likely voters in the state, has a margin of error of 5 percentage points, Brad Coker of the Washington, D.C.-based Mason Dixon Polling and Research Inc. said Sunday.

Besides New Mexico, Mason-Dixon polled several Western states including Colorado, Arizona, Nevada, Utah and Wyoming between Aug. 13 and 15.

Sunday's poll is the first in recent weeks showing McCain ahead in New Mexico. Last week, a Rasmussen Reports poll of likely voters in New Mexico showed Obama leading McCain 47 percent to 41 percent.

In other states, McCain was ahead of Obama by only one point. However, in another battleground state, Nevada, McCain led by a seven-point margin. McCain had wide leads in his home state of Arizona and traditional Republican states Utah and Wyoming.

The Mason-Dixon poll showed Gov. Bill Richardson, while maintaining respectable approval numbers among state voters, was not rated as high as other Western governors.

Richardson was rated "excellent" by 18 percent of those polled, "good" by 38 percent, "fair" by 21 percent and "poor" by 22 percent.

His 56 percent combined good and excellent rating is below the 82 percent favorable rating for Utah Gov. Jon Huntsman, Wyoming Gov. Dave Freudenthal's 81 percent, Arizona Gov. Janet Napolitano's 66 percent and Colorado Gov. Bill Ritter's 60 percent.

The only Western governor who did worse than Richardson is Nevada's scandal-plagued Gov. Jim Gibbons, whose total favorable rating was 23 percent.

Coker said Richardson's ratings have fallen among Republican voters. In the past, the governor has enjoyed relatively strong GOP ratings, even winning an estimated 25 percent of the Republican vote in his 2006 re-election.

Coker said the lower Republican ratings probably are a result of Richardson's presidential campaign.

"When someone who has strong bipartisan support steps into the national spotlight, it often causes a loss of support from the other party," Coker said. "It's happened to a certain extent with McCain among Arizona Democrats.

"It happened to (former U.S. Sen.) Bob Graham in Florida when he briefly ran for president in 2004. It happened to Harry Reid in Nevada after he became Senate majority leader."

Coker said when a moderate Democrat with bipartisan support runs for president, appealing to the more liberal Democratic base who vote in the Iowa caucuses and New Hampshire primary, it causes loss of Republican approval.

The poll also asked several issues-oriented questions.

One of the more surprising results showed New Mexicans — as is the case in other Western states — is divided on the reality of global warming.

Only 48 percent said climate change was a scientific reality, while 44 percent said the matter was still unproved and open to debate. Across the region, 49 percent believe in global warming, while 46 percent said it's unproved.

On the issue of domestic oil drilling — a question that's been front and center in the U.S. Senate race between Democrat Tom Udall and Republican Steve Pearce — 63 percent of those polled in New Mexico say they support drilling for oil and gas on public lands, while 24 percent are opposed. Asked what should be the higher priority, drilling on public lands to find new energy sources or protecting the environment, 45 percent said drilling while 39 percent said protecting the environment.

In another question, 67 percent of New Mexicans said they'd be willing to pay more for cleaner renewable energy. Only 22 percent said they wouldn't be willing to pay more.

On the issue of immigration, 64 percent said they favor strong efforts to stop illegal immigration from Mexico — including building a border fence and cracking down on employers who hire undocumented workers.

But asked whether undocumented Mexicans should be allowed to apply for citizenship or be deported, 57 percent said they should be allowed to apply for legal status, while 35 percent said they should be deported.

Contact Steve Terrell at 986-3037 or sterrell@sfnewmexican.com.