Rep. Ed Markey's (D-Mass.) Senate campaign is up with a tough new ad that mentions the tragedy in Newtown, Conn., while attacking his opponent's position on gun control.

"And Gomez is against banning high-capacity magazines like the ones used in the Newtown school shooting," says the narrator, before video plays of GOP candidate Gabriel Gomez expressing opposition to the ban.

Republicans quickly pounced on the ad, arguing that it politicizes the tragedy in Newtown.

Markey is favored to win the seat formerly held by Secretary of State John Kerry (D-Mass.), but polling has shown that the race might be competitive.

Update: Gomez is also out with a new ad -- his first of the general election. It's a pretty straight biographical ad.