Like many of his other views and policies, Sen. John McCain's approach to science, technology and environmental issues doesn't always fall within party lines. But critics say they aren't always consistent, either.

Science-policy wonks have generally regarded the Arizona senator as the best option among the Republican presidential candidates. But as McCain fights to solidify his status as a front-runner in the Republican race, at least one environmental group accuses McCain of changing positions to appease the GOP base – the very charge McCain's been trying to pin on rival Mitt Romney.

"It appears that he's made a significant change in his position, which we find quite troubling," says Tony Massaro, political director with the League of Conservation Voters.

Massaro points to a bill McCain co-sponsored with Sen. Joe Lieberman (D-Connecticut), which they've been trying to enact for several years. The Climate Stewardship and Innovation Act of 2007 would reduce the emission of greenhouse gases 65 percent by 2050. The targets are mandatory, achieved through a market-based cap-and-trade system, wherein polluters buy and sell a limited number of emissions permits.

When Lieberman reintroduced the bill last year, McCain reiterated his support, arguing for "rational, mandatory emission-reduction targets and timetables." He lauded a similar measure under consideration in California.

But when MSNBC anchor Tim Russert asked McCain last week whether he favors "mandatory caps," he denied it. "No. I'm in favor of cap-and-trade."

"He's been by far the best Republican on this issue until he made that statement last week," Massaro says.

In other technology-related legislative efforts, McCain – like colleagues in both parties – has also sponsored feel-good online child-safety legislation of questionable effectiveness.

On McCain's campaign website, he touts his sponsorship of legislation that would require the establishment of a national online registry of sex offenders convicted of crimes against children. The legislation would require those sex offenders to register all their e-mail addresses, instant-messenger screen names and other online identities with the authorities. Failure to do so would land them back in prison for 10 years.

Groups such as the Center for Democracy and Technology have said the legislation is harmless, but useless.

"Like a lot of these other proposals to protect kids on Capitol Hill, this e-mail registration proposal is something that superficially sounds like a good idea, and a politician can claim to have sponsored legislation to protect kids," says John Morris, senior counsel at the Center for Democracy and Technology. "In fact, it almost does nothing to protect them."

A more sensible bill in the House, Morris says, jettisons the online identifier concept, and instead requires convicted sex offenders on probation or parole to install filtering software on their computers that would block access to sites where children congregate. The offender's computer use and the settings on that software would be monitored by his probation or parole officer.

"Although they started off in the same place, Congressman Pomeroy (the sponsor of the House bill) shifted gears, and they now have a bill that actually targets the sex offenders who are problems instead of this general blunderbuss approach which will not be effective and is in fact window dressing," Morris says.

McCain scores higher points with business technologists. Michael Arrington, the editor of the influential blog TechCruch, recently endorsed McCain for supporting H1-B temporary work visas for programmers, among other pro-business moves. (Arrington endorses Democratic Sen. Barack Obama as well).

And Gigi Sohn, co-founder of the public interest lobbying group Public Knowledge, says McCain has proven willing to take stances against the well-funded incumbent telecommunications companies in legislative battles.

Sohn also gives McCain points for joining with Public Knowledge to kill a section of the 2005 Family Home Movie Act that could have made it illegal for consumers to fast forward through commercials while watching their DVRs.

"He likes being considered a friend of the consumer," Sohn says. "If you're a pro-balanced copyright person, you're for the ability to make personal uses of the works that you buy."