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 KerryLobbying world Kerry: Trump not pursuing 'smart' or 'clever' plan on North Korea Tillerson will not send high-ranking delegation to India with Ivanka Trump: report 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 strategist donates to Alabama Democrat McConnell names Senate GOP tax conferees Brent Budowsky: A plea to Alabama voters MORE (R-Ky.) sending out a fundraising letter on his behalf last week.