US Representative Edward J. Markey, who has repeatedly called on Republican Gabriel E. Gomez to sign a pledge curbing third-party spending in their Senate race, knows from personal experience how difficult it is to renounce outside contributions.
Markey himself pledged in 1984 not to accept contributions from political action committees, but put that promise aside in 2003 after Congress tightened campaign finance laws and as the congressman contemplated the possibility of replacing Senator John F. Kerry, who was then running for president.
Between 2003 and 2012, the Malden Democrat received $2.7 million from political action committees, about a third of his total haul during that time.
Between Jan. 1 of this year and April 10 — 20 days before the Democratic primary that Markey won last week — PACs gave him more than $500,000, according to a Globe analysis of Federal Election Commission data.
Markey’s pledge three decades ago and the current proposed pledge apply to different types of contributions, but both represent well-funded outside forces trying to influence elections and policy.
The PAC donations that Markey once shunned go directly into his campaign account and require FEC disclosure.
The People’s Pledge, which Scott Brown and Elizabeth Warren famously endorsed in their Senate campaign last year, discouraged advertising on behalf of either candidate by super PACs, a newer fund-raising vehicle that can raise unlimited money, and nonprofit groups, which do not have to reveal donors.
Markey has devoted much of his energy since winning last week’s primary to publicly urging Gomez to sign the pledge and has made campaign finance policy a calling card of his congressional portfolio.
“Everything and every contribution I have ever taken is completely disclosed, and it is limited, so the public can decide who, in fact, has given money and whether or not they want to vote for me,” Markey said at a Monday press conference.
“Here, Gabriel Gomez is now saying he’s willing to accept unlimited and undisclosed money, so it’s impossible for the voters of the state of Massachusetts to, in fact, know who is supporting him.”
For decades, Markey has hauled in large amounts from the communications and electronics industries, which he helped oversee during 20 years as either chairman or ranking Democrat of the House Subcommittee on Telecommunications.
Between 1989 and 2012, most of which time Markey spent highly ranked on the committee, $2.5 million of the $12 million Markey raised came from those two industries, nearly $1 million of it from PACs after he dropped the pledge, according to the nonpartisan watchdog Center for Responsive Politics.
Over the same period, lawyers and lobbyists kicked in $2.2 million, about $322,000 of it through PACs.
That stretch of time was marked by groundbreaking advances in technology that demanded decisions in Washington about how to regulate the burgeoning new media industry.
Markey aides point to analyses by groups such as Sopatrack, which tracks the correlation between donations based on legislation and Congress members’ votes, finding that Markey voted with a majority of his donors only 51 percent of the time.
“No one has fought harder for competition and for consumers within those industries than Ed Markey,” said his spokesman, Mark Horan, referring to the industries that had donated most heavily.
Horan said Markey opted out of the hard line against PAC money after the 2002 enactment of the McCain-Feingold Act, which banned “soft money” — unregulated donations to political parties that could then be redistributed to candidates.
“When McCain-Feingold passed, it set reasonable rules of the road for campaign finance,” Horan said. “He thought that since PAC money was limited and disclosed and because money like soft money was made illegal, it was an appropriate time to do so.”
Markey’s first television ad of the general election, which began airing on Wednesday, emphasizes that he co-wrote legislation that broke up telecommunications monopolies, paving the way for modern technologies and social media.
“He’s taking credit in that ad for opening up competition in communications, which helped create hundreds of billions of dollars in new investment and new jobs,” Horan said.
Those same industries helped him amass a war chest of $3.1 million by the beginning of the Senate race.
“What’s clear here is that this is somebody who has used his position in Congress well to raise money, and you can see a clear connection between the committee he chaired and the people who are making donations to him,” said Kathy Kiely, managing editor for the Sunlight Foundation, another nonpartisan campaign and government watchdog.
Gomez has refused to take the pledge, arguing Markey has served in Congress since 1976 and thus has a decadeslong head start on fund-raising.
The pact would discourage spending on advertising by outside groups by requiring whichever candidate is intended to benefit to pay 50 percent of the outside group’s outlay to a charity of the other campaign’s choice.
After Warren and then-Senator Brown signed the deal last year, it was widely hailed as a landmark defense against the type of negative, shadowy funded advertising common in recent years after courts ruled in favor of unshackling campaign finance.
About 80 percent of ads in a similar race in Ohio that did not have a pact were negative, the study found.
A study released last week by Common Cause found that just 9 percent of total spending in the Brown-Warren race flowed from outside groups, and none of it for TV ads after the two rivals signed the pledge.
Less than 40 percent of the ads in last year’s campaign were negative, the study concluded.
Markey’s decision to highlight Gomez’s refusal has solid strategic footing.
At a press conference on Monday, Markey suggested a list of likely antagonists who would air ads against him, including Karl Rove, the National Rifle Association, and the oil lobby.
That strategy, of tying Gomez to national conservatives, echoes previously successful campaigns against Massachusetts Republicans.
With Gomez trailing Markey in the most recent fund-raising report, with roughly $500,000 on hand to Markey’s $4.6 million, the congressman also knows that he can afford to project a good-government image.
If outside groups sympathetic to him decide to capitalize on a pledge-free race later on, Markey can claim he tried to prevent such interference.
Markey has refused to say whether he would take the pledge unilaterally, but advisers call it unlikely.
A Suffolk University/7NEWS poll released on Wednesday reflected heavy support for the People’s Pledge, with roughly 71 percent of likely voters calling it a very or somewhat important matter in the campaign.
Markey himself has benefited from heavy outside spending during the campaign. Over $2.1 million in outside spending came into Massachusetts before the primary, the vast majority of it designed to help Markey’s campaign.
Markey and his primary opponent, Representative Stephen F. Lynch, signed on to the People’s Pledge, but that did not prevent nonadvertising spending by outside groups.
The League of Conservation Voters spent over $468,000 in support of Markey between Feb. 20 and April 25, paying for polling, fliers, T-shirts, and computers, according to the Sunlight Foundation. Its super PAC, the LCV Victory Fund, spent over $360,000, most of it for field canvassing and consulting.
The NextGen Committee, a super PAC formed by California billionaire Tom Steyer, spent nearly $360,000 in its effort to blast Lynch for his support of the controversial Keystone XL pipeline. Of that spending, more than $100,000 was on aerial banners, which was not covered under their pledge.
Markey denounced Steyer’s interference, saying “these kinds of tactics have no place in our political discourse and should be repudiated.”
The Markey campaign made a $2,000 charitable contribution to Lynch’s charity of choice after reports that Steyer also paid for online ads bashing Lynch.
Markey also benefited from nearly $320,000 in spending by the Service Employees International Union PAC.
Gomez picked up $93,000 in support from the Committee for a Better Massachusetts, a super PAC advised by Eric Fehrnstrom, a longtime aide to former Massachusetts governor and 2012 presidential nominee Mitt Romney.
Of the more than $500,000 Markey raked in from PACs between Jan. 1 and April 10, the most recent data available, the communications and electronics sector was the most generous, chipping in $142,500, according to a Globe analysis.
PACs identified as ideological or devoted to a single issue gave $120,356.
Lawyers and lobbyists sent in $59,000.
The health sector donated $52,100.
Markey has called his vote in favor of the 2010 health care expansion law “the proudest vote of my career.”
Within the communications and electronics sector, Hollywood has been particularly generous to Markey, donating over $1 million between 1989 and last year.
Globe staff contributed. Jim O’Sullivan can be reached at James.OSullivan@globe.com. Follow him at @JOSreports.