The Democratic Senatorial Campaign Committee is spending about $750,000 backing an ad that charges Gomez "supports protecting special tax breaks for corporations and multimillionaires like himself." 

It also notes his support for raising the retirement age and cuts to Social Security. That stems from his backing a provision, proposed by President Obama, that would change the way Social Security benefits are calculated and subsequently lower those benefits for many.

"Gabriel Gomez puts himself ahead of us," a narrator says.

Senate Majority PAC is spending about $500,000 on its ad, which repeats similar attacks, charging, "If you're worried about your retirement, then you can't trust Gabriel Gomez."

The focus on issues relevant to seniors reflects the fact that they are typically the demographic group to turn out on Election Day, and during a low-turnout special, their support will be significant.

In addition to the attack ads, billionaire Tom Steyer's group launched a new canvassing effort focused on voters in low-income areas and communities of color in Boston to raise awareness of the upcoming special election.

The campaign is targeting 44,000 Democratic voters in the city, an effort to give Democrat Edward MarkeyEdward (Ed) John MarkeyOvernight Regulation: FTC launches probe into Equifax | Dems propose tougher data security rules | NYC aims to slash greenhouse gas emissions | EPA to reconsider Obama coal ash rule Overnight Cybersecurity: Kaspersky to testify before House | US sanctions Iranians over cyberattacks | Equifax reveals flaw that led to hack Dems propose data security bill after Equifax hack MORE a cushion of support from his base for the election.

Though he's favored to win Secretary of State John KerryJohn Forbes KerryBringing the American election experience to Democratic Republic of the Congo Some Dems sizzle, others see their stock fall on road to 2020 The Hill's 12:30 Report MORE's (D) former seat, Gomez has kept Markey's lead to single digits in nearly every poll of the race, and Democrats insist they're taking nothing for granted. 

This is the most significant influx of outside help yet for Markey, who began his general election campaign hammering Gomez for refusing to sign a pledge to keep outside money out of the race.

Gomez has yet to receive substantial support from the National Republican Senatorial Committee or outside GOP groups, though the Massachusetts Republican Party joined his campaign on an ad buy that Democrats have suggested was funded by the NRSC.

The memory of the 2010 special Senate election, which brought Scott Brown to the Senate, still looms large in the minds of Massachusetts Democrats.