With the presidential circus having left their backyard, New Hampshire’s Senate candidates lost little time this week digging into each other’s commitment to limiting spending in what’s expected to be one of the most competitive and expensive Senate races in the country.

Just days after Vermont Sen. Bernard Sanders won the New Hampshire Democratic primary with 60 percent of the vote — a presidential race in which he’s made campaign finance a big issue against Hillary Clinton — Republican Sen. Kelly Ayotte came out with a surprising campaign finance proposal of her own.

“Campaigns don’t have to be driven by third-party groups — we can change the status quo and take a stand to say that this race should be about New Hampshire,” she wrote to her Democratic rival, Gov. Maggie Hassan, in challenging her to sign a “People’s Pledge” to limit outside spending in their Senate race.

On Friday, Hassan went one step further, signing and sending to Ayotte a “Strengthened People’s Pledge” that would require candidates to limit their campaign spending to $15 million. Although Hassan’s quarterly fundraising is on par with Ayotte’s, the incumbent has a significantly larger war chest.

Democrats in Washington responded to Ayotte’s pledge by accusing her of trying to cover up the third-party money that’s already been spent on her behalf and speculated that perhaps she’s trying to pre-emptively cut off similar outside groups from supporting Hassan. The Hassan campaign quickly pointed out that outside groups supporting Ayotte spent an additional $187,000 on independent expenditures on Feb. 11 — the same day Ayotte issued her pledge.

Democrats estimate GOP outside groups have spent roughly $5 million supporting Ayotte or attacking Hassan. So far, Senate Majority PAC has spent $600,000 for Hassan, although Republicans argue that more outside spending on Hassan’s behalf must be coming since the Hassan campaign on Feb. 7 posted B-roll on its YouTube page.

Just as Democrats were quick to paint Ayotte as a hypocrite on Friday by calling into question her legislative commitment to campaign finance reform, Republicans salivated Thursday, waiting to call out Hassan for breaking with her previous criticism of outside spending — and with her party’s liberal standard bearers.

“It’s disappointing that Governor Hassan’s first reaction to the People’s Pledge wasn’t to sign it — but rather to launch more ugly attacks,” said Ayotte campaign manager John Kohan in a statement. “If this pledge was good enough for Jeanne Shaheen and Elizabeth Warren, why isn’t it good enough for Maggie Hassan?”

“Hassan almost has to sign the pledge or it will enrage her base,” said Ryan Williams, a consultant to the New Hampshire GOP. And even beyond liberals, Williams added, “Most average voters would probably enjoy a reduction in political advertising given that they’ve been pummeled with ad after ad from super PACs during the presidential cycle given our first-in-the-nation status.” Ayotte, herself, got dragged into the presidential air war — an incident to which she alluded in her letter to Hassan.

But some Democrats question why Ayotte would want to initiate a pledge in the first place. “You only do something like this if you’re legitimately scared about being outspent, and nine out of 10 political operatives will say that fear should not exist if you’re a Republican because that’s not the world we live in,” a Democratic operative said.

Republicans, however, think that the pledge will resonate with New Hampshire voters.

“It’s not the biggest issue on people’s minds, but it’s an issue that’s come up in New Hampshire in previous election cycles,” Williams said. “She’s demonstrating her independence by offering to take this pledge,” he said of Ayotte.

As one of the most vulnerable incumbents this cycle, Ayotte has recently tried to stake out more moderate positions on issues such as the administration’s clean power plan, for example, to appeal to independent voters.

For Hassan, the Democratic operative said, signing the pledge would be an opportunity to cut off the Koch brothers, whose Americans for Prosperity network hit the airwaves against Hassan before she even got in the race.

The People’s Pledge, which requires a candidate who benefits form third-party advertisements to donate 50 percent of the ad’s cost to a charity chosen by the opposing candidate, has its roots in New England. Then-Massachusetts Sen. Scott Brown, a Republican, and Warren, his Democratic opponent, signed the pledge in 2012. And while it didn’t keep outside money out of the race completely, reports from nonpartisan watchdog groups have found that outside spending paled in comparison to other competitive Senate races that cycle.

Warren ended up raising and spending more money than Brown, who went on to lose the race by 8 points. When Brown ran for Senate in New Hampshire against Shaheen in 2014, she called on him to sign a similar pledge; he demurred. Brown went on to lose that race, too.

This cycle, it’s usually been Democrats who have called on their opponents to sign pledges. Former Sen. Russ Feingold, a Democrat, called on Sen. Ron Johnson, a Republican, last summer to sign a similar “Badger Pledge” in Wisconsin to keep super PACs out of their race. Johnson hasn’t agreed and has instead gone after Feingold — a champion of campaign finance reform — for a report that his Progressives United PAC spent most of its money on overhead and salaries rather than helping to elect progressives.

Pledges have come up in Democratic primaries, too. In Maryland’s Senate primary, Rep. Donna Edwards rejected the “Free State Pledge” offered by fellow Democratic Rep. Chris Van Hollen, who has consistently led in campaign fundraising. Edwards has benefited from outside spending from EMILY’s List. In Florida, Democratic Rep. Alan Grayson, who has plenty of his own money to spend on the Senate race, floated the idea of a pledge to fellow Rep. Patrick Murphy. “This is not a serious conversation with Alan Grayson,” Murphy’s spokesman said at the time.

Contact Pathé at simonepathe@rollcall.com and follow her on Twitter at @sfpathe .

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