The ads will begin running on Wednesday, the day Markey and Gomez meet for a debate in Boston.

Reports said Markey is also launching his own ad buy this week, spending $631,000.

The ad buys come as polls show Markey expanding his lead in the contest to fill Secretary of State John KerryJohn Forbes KerryJuan Williams: Trump's dangerous lies on Iran Pompeo: US tried, failed to achieve side deal with European allies Trump administration braces for big week ahead in foreign policy MORE’s former seat.

An Emerson College poll released in late May showed Markey with 45 percent support to Gomez’s 33.

Markey has sought to nationalize the race, tying Gomez to the national GOP and charging that the Republican contender would obstruct President Obama’s agenda if elected to the Senate. 

Gomez has sought to stress his independence in the strongly Democratic state, telling reporters on Monday that “one of the things I am going to change in Washington is my own party.” 

Republicans though have rallied behind Gomez, with Senate Minority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellGOP lawmakers want Trump to stop bashing Congress Parkland father calls out Trump, McConnell, Ryan after Santa Fe shooting Overnight Finance: House rejects farm bill in conservative revolt | NAFTA deal remains elusive as talks drag on | Dodd-Frank rollback set for House vote MORE (R-Ky.) sending out a fundraising letter on his behalf last week.