As he traveled across New Hampshire in early June 2014, Republican candidate Scott Brown sounded an alarm on U.S. Sen. Jeanne Shaheen’s views on energy policy.

Brown warned that Shaheen, a Democrat who faces re-election in the fall, is pushing for a "national energy tax."

The claim was repeated on Brown’s website and in a series of press releases from his campaign, and was reiterated in an op-ed published during his "making energy affordable" tour.

Brown said he supports a variety of measures to make energy more affordable without passing "Sen. Shaheen’s national energy tax."

With the New Hampshire Senate race drawing national attention, it wasn’t long before Brown’s comments were scrutinized.

Judy Reardon, Shaheen’s chief counsel, issued a challenge to Brown’s campaign on Twitter, asking the former Massachusetts senator to provide evidence that Shaheen supports a "national energy tax."

"Please cite the vote," she wrote in a June 9 message .

Brown’s campaign manager, Colin Reed, shot back in a press release that he found it troubling Shaheen’s staff didn’t remember Shaheen’s votes in Congress.

"The simple fact is that one year ago, Sen. Shaheen voted for a measure that would have amounted to a new national energy tax which would have a disastrous impact on New Hampshire’s economy," Reed said.

With Brown and Shaheen sparring on energy policy, we decided to delve deeper into the issue. We were curious about whether Shaheen’s record indeed showed support for an energy tax or carbon tax, as taxes on oil, gas and coal usage are sometimes called.

The logic behind the tax is that by making natural resources costlier for individuals and businesses to use, a carbon tax would encourage the use of alternative energy sources.

Most economists agree that a carbon tax would be effective, but the issue hasn’t gained much political traction.

We began by asking Brown’s campaign to explain his statements. Brown campaign staffer Elizabeth Guyton pointed us to Shaheen’s vote on a 2013 budget resolution put forth by Sen. Sheldon Whitehouse, D-R.I., who has expressed support for implementing a carbon tax.

The resolution stipulated that revenue generated by any future carbon tax must be given back to the public in some form.

Shaheen voted in favor of the budget resolution, though nothing in that amendment would actually enact a carbon tax. Rather, the amendment offered a rough framework for how money generated from such a tax, if one were enacted, would be put to use.

"I think that ultimately a fee on carbon pollution is inevitable, and the purpose of that amendment was to begin a discussion on that and begin the discussion about when that happens, what the best way to use the proceeds of the fee are," Whitehouse told reporters in September. "So from that point of view, I didn’t view it as binding anybody on a carbon fee, but I did view it as an assessment of the best way of using carbon fee proceeds."

Although she was allying herself with a carbon tax supporter’s amendment, Shaheen’s vote wasn’t directly in support of a carbon tax.

The second piece of evidence offered by Brown’s campaign concerns an amendment proposed by Sen. Roy Blunt, R-Mo. Blunt has emerged as a persistent carbon tax opponent in the Senate.

In 2013, Blunt proposed an amendment that would have increased the threshold for passing a carbon tax framework within the budget resolution to 60 votes.

Shaheen voted against this amendment, even as some of her Democratic colleagues from energy producing states voted for it. Still, by voting against Blunt’s measure, Shaheen wasn’t directly expressing support for a carbon tax.

Shripal Shah, a spokesman from Shaheen’s Senate office, said that Shaheen has never supported a carbon tax. In an email, Shah wrote that Shaheen supports "market-driven solutions" to address pollution, such as the Regional Greenhouse Gas Initiative.

This statement seems to fall in line with the position Shaheen took when she first campaigned for the Senate in 2008. During a roundtable discussion at Seacoast Energy Alternatives in Somersworth, New Hampshire, Shaheen said she would prefer a cap-and-trade program over a carbon tax because it’s "easier to sell to the population" and "puts the onus" on the polluters.

When it comes to the legislative record, Shaheen’s efforts to influence energy policy since taking office have been focused largely on boosting energy efficiency.

Shaheen partnered with Sen. Rob Portman, R-Ohio, to craft an energy efficiency bill that would launch a federal training program for energy-efficient building design and operation and establish a loan program for energy improvements to homes and small businesses, among other initiatives.

The bill has twice died in the Senate. The most recent effort failed on May 12, 2014, when supporters failed to reach the 60 votes necessary to close debate on the bill and proceed to a final vote.

Shaheen took to the Senate floor after it became clear the measure would not pass to remind her colleagues that energy efficiency is the cheapest, fastest and cleanest way to address the country's energy demand.

"One of the things that I like about energy efficiency is that it doesn’t matter whether you support fossil fuels or whether you support alternative sources of energy," she said. "Everyone benefits from energy efficiency."

Our ruling

Brown’s campaign said that Shaheen voted for a measure that would have amounted to a new national energy tax.

The campaign cited Shaheen’s support for a 2013 amendment that would have established guidelines for any future carbon tax. They also pointed to Shaheen’s vote against legislation that would have made it harder to pass a carbon tax framework.

Shaheen’s campaign told us Shaheen has never supported a carbon tax, and we didn’t find any evidence to contradict that. One of her major legislative efforts, the Shaheen-Portman bill, focused on energy efficiency.

Brown has a point that Shaheen voted for a revenue plan offered by a carbon tax supporter and shrugged off a proposal from a carbon tax opponent. Still, neither of those positions is the same as voting for a new energy tax.

We rate this claim Mostly False.