The year was 2013 and Edward J. Markey was a huge fan of the People's Pledge — going so far as to hold a news conference with an empty chair to hammer his Republican opponent for refusing to sign the pact that would limit outside spending in the Massachusetts Senate race.
On Monday, there was another news conference about the People's Pledge. Only this time, Markey was the one missing from the picture. And the two Democrats hoping to unseat him were doing the hammering.
"Several years ago, when it was in his interest to ask for all outside money to be kept out of campaigns, Senator Markey cared strongly enough about this issue to call outside money 'political pollution.' Today, not so much," said Shannon Liss-Riordan, a labor attorney, quoting Markey from his 2013 race.
The Brookline Democrat, who gained a national reputation for her legal battles on behalf of workers against Amazon, Google, FedEx, and Starbucks, attributed Markey's new reluctance on the issue to "political expediency."
Liss-Riordan and Representative Joseph P. Kennedy III on Monday signed their names to a pledge that closely resembles the one Markey backed in 2013. The pact the two signed Monday says that if any third-party group runs a TV, radio, or digital ad or sends direct mail during the primary, the candidate who benefits must donate half of the ad's cost to a charity of the other two opponents' choosing.
The pledge would only kick in if all three candidates sign. So far, Markey has declined.
Instead, Markey proposed his own watered-down pledge via news release late Monday morning, a few hours after his opponents announced their event. Both the Liss-Riordan and Kennedy campaigns said they learned about Markey's proposal from news reports.
The key difference with Markey's plan: His would allow for some third-party advertising in the race, rather than ask all groups to abstain. Markey's proposal would bar "all outside negative advertising" but would allow certain outside groups, who disclose their donors, to disseminate "positive" ads and messages in support of one of the candidates.
In a statement, Markey said while it is important to keep negative ads and dark money out of politics, "we also need to make sure progressive organizations have the right to make their voices heard in this critical election."
He said his version "recognizes that our democracy is made healthier and more inclusive when these voices are heard."
Notably, Markey has a lot of support from outside groups, including Environment Massachusetts, a statewide environmental advocacy organization that has pledged to spend $5 million to support Markey's campaign.
"The idea that you have this positive message — that is a loophole big enough to drive a truck through," Kennedy told reporters at the signing event in Boston on Monday.
He also rejected Markey's idea that certain outside groups should be able to pour unlimited resources into a race even if Democrats broadly agree with the policy positions those groups profess.
"If you believe that there's too much money involved in politics, then we should all do our part to get that money out, that's what this is," Kennedy said.
While Markey said his proposal would only allow groups that disclose their donors to run ads, the other campaigns said his measure would still allow super PACs and other third-party groups to find loopholes and pump money into the race without sharing the true source of the cash.
"This doesn't need to be a big money race," said Liss-Riordan, who has put $3 million of her own money into her campaign.
"Massachusetts voters should be deciding this race not who has most outside money supporting them."
The political impact of this ongoing campaign finance feud is unclear. Both sides said they hoped the other would come around to their view. In the meantime, none are under any obligation to discourage outside groups from getting involved.
What is clear: While the high-profile face-off between Markey and Kennedy hasn't produced much in the way of fireworks so far, there's plenty of tension between the campaigns of two men who had long been on friendly terms.
At the end of September, each of the candidates already had a significant stockpile of cash in the bank: Markey had $4.4 million, Kennedy had $4.3 million, and Liss-Riordan had $2.8 million, federal filings show.
Kennedy first proposed candidates in the race sign a pledge modeled after the one Elizabeth Warren and then-Senator Scott Brown inked in their divisive 2012 race. Their agreement called on all outside groups, other than political parties, to stop spending money to support either candidate.
A campaign finance watchdog, Common Cause, later reported that the pledge significantly reduced spending by outside groups and the number of negative ads in the campaign.
Markey has stayed relatively mum on Kennedy's proposal ever since the Newton Democrat first pitched it back in September, even after the other two candidates in the race said they would participate. (Steve Pemberton, the other Democrat running at the time, has since dropped out of the race.)
By contrast, Markey has been an enthusiastic believer in the People's Pledge in the past. In the 2013 special election race to fill the Senate seat that opened up when John Kerry became secretary of state, Markey called such a pledge "key" so voters know who is supporting each candidate, since outside groups do not have to disclose their donors. He repeatedly criticized his Republican opponent, Gabriel E. Gomez, for declining to sign the pledge.
The Kennedy and Liss-Riordan campaigns say they've tried to work with the Markey campaign to get the Malden Democrat on board — but to no avail.
One Kennedy aide said Markey's team had not responded to a single e-mail between the three campaigns in recent weeks discussing the subject.
Victoria McGrane can be reached at victoria.mcgrane@
globe.com. Follow her on Twitter @vgmac.