U.S. presidential hopefuls Sen. Barack Obama, D-Ill., and Sen. John McCain, R-Ariz., may not sound much different when they talk about their energy and emissions goals, but at a packed forum Wednesday night in San Francisco, their campaign representatives took slightly different stances on the question of state versus federal rights - and those positions could impact the future of greentech.

Take the clash between the state of California and the U.S. Environmental Protection Agency. The Golden State has gone to court many times to try to win a waiver that would allow it to enforce stricter vehicle-emissions standards than the current federal requirements set by the EPA.

At the Renewable Energy Forum, Tim Carmichael, a senior campaign advisor for Sen. Barack Obama, and Kurt E. Yeager, California co-chair of the McCain Energy Coalition, fielded questions about how their administrations would deal with states that want to advance their own energy agendas.

Would McCain or Obama find himself fighting with states while carrying out his own respective energy plan?

A question posed to Carmichael and Yeager during the question-and-answer session asked whether the candidates would reverse a decision by the U.S. Environmental Protection Agency last December to deny a request by California on regulating tailpipe emissions.

California requested a waiver of the Clean Air Act so that the state could set its own stricter vehicle emissions standards (see EPA Rejects California Vehicle-Emission Standards). But the head of the EPA and President Bush deferred to the federal government, not to the states, to set the rules for greenhouse gas emissions.

"The question is how to have an effective strategy," said President Bush after the EPA decision. "Is it more effective to let each state make a decision as to how to proceed in curbing greenhouse gases or is it more effective to have a national strategy?"

Carmichael said Obama opposes the EPA decision. "Sen. Obama believes strongly that there is no good that will come from holding back innovations and leadership at the state level," said Carmichael, who is the senior director at the Coalition for Clean Air, a nonprofit focusing on air quality issues in California. "If states like California want to push for clean vehicles ... why should the federal government hold them back?"

Yeager, however, said that while McCain "wouldn't appoint someone who doesn't support the states to show leadership," California's attempt to set its own emissions standards isn't a smart move.

"The federal government should take the lead," said Yeager, the executive director of the nonprofit Galvin Electricity Initiative and retired head of the Electric Power Research Institute, which represents American utilities. "People aren't able to build cars for a single standard even for a state as large as California."

On the issue of offshore drilling, both candidates defer to the states for creating more drilling opportunities. McCain has shown a strong support for drilling for oil and gas while Obama has not.

"He's not proposing something that will override the decision of a state," Yeager said.

Although Obama is "not a fan" of offshore drilling, he plans to support a federal bill that would allow southeastern states such as the Carolinas and Georgia to do so as long as the governors go along, Carmichael said. "As a compromise that would bring a lot of good things ... he feels he should support it."

These positions on states' rights could impact issues beyond California's emission battle and offshore drilling, as well.

Clashes between states and the federal government over environmental or energy issues are not uncommon. A case brought by North Carolina to challenge the federal Clean Air Interstate Rule resulted in a recent court decision that tossed out the rule, saying the federal government overstepped its authority to regulate certain types of power-plant emissions (see Court Rejects EPA Rule).

An increasing number of states and local governments have passed their own tax incentives and grants to achieve certain clean energy and greenhouse gas emissions mandates (see California Offers Plan to Clean the Air, Massachusetts Passes Sweeping Energy Bill and Pennsylvania Governor to Sign $650M Energy Bill).

In the end, whether Obama or McCain would make a friendlier ally to the states or the renewable energy business is still a toss up. Both have presented themselves as proponents of greentech for electricity generation, biofuels and hybrid-electric cars.

Although they offer different approaches to reach those clean energy goals, those details aren't likely to make a difference when either one becomes the next president, according to a piece by the National Public Radio that was broadcast the same day that Carmichael and Yeager spoke.

On NPR, economist Joe Aldi at think tank Resources for the Future put it this way: "One can quibble with some of the details, but at end of the day, the difference between them will get washed out by negotiations between the next president and the Congress."