(CNN) – The U.S. Senate race in Massachusetts took a nasty turn this week when the Republican candidate equated his Democratic rival to "pond scum" for a web video that pictured him on screen with Osama bin Laden.
Saying he couldn't think of anything more offensive, Gabriel Gomez told a reporter he was worried his four kids would see the ad, which hits Gomez for his work with a group that accused President Barack Obama of "politically capitalizing on U.S. national security operations and secrets" after the bin Laden raid.
"For him to be as dirty and low - pond scum - to put me up there next to bin Laden, he's just got to be called what he is," Gomez, a former Navy SEAL, said of Democratic Rep. Ed Markey.
The video was originally posted in early May. Titled "Meet Gabriel Gomez: Just Another Republican," the spot shows a clip from MSNBC where Gomez and an image of the September 11, 2001, terrorist mastermind are displayed side-by-side. In the clip, Gomez is seen defending OPSEC Education Fund, which criticized Obama after bin Laden's death.
The controversy came days after each candidate won his party's nomination to contest for the open Senate seat left vacant when John Kerry became secretary of state. The two will compete in the special election on June 25. William "Mo" Cowan is currently serving as interim senator, appointed by Democratic Gov. Deval Patrick.
Following April's Boston Marathon bombings, the race largely dropped off newspaper front pages in the state. The candidates suspended campaigning for nearly a week following the attack.
But as Election Day approaches, the race is regaining momentum, with each candidate launching bitter attacks in a bid to woo voters-or dissuade them from the other candidate. The most recent polls in the contest have Markey ahead of Gomez, ranging from a single digit advantage to a double digit lead.
But Republicans still see an opening in the state, which has long voted for Democratic presidential candidates but has shown more willingness to elect Republican governors. In 2010, the state voted Republican Scott Brown to the Senate in a special election, though he lost his re-election bid last year.
The National Republican Senatorial Committee has sent multiple staffers to the state in recent days, including senior adviser Kevin McLaughlin, in a bid to bolster Gomez in the final month before ballots are cast.
On Friday, a Markey spokesman said the pond scum remark was a "new low" for Gomez.
"His desperate attack will do nothing to distract from his opposition to an assault weapons ban and limits on high-capacity magazines," Markey spokesman Andrew Zucker said.
Democrats, in turn, point to Gomez's refusal to release his 2005 tax return, which they say will further illuminate a tax break he took for agreeing not to alter his historic home. It turns out the local historic preservation board already prohibited any changes.
Weeks after Gomez took the deduction, which was for more than $200,000, the Internal Revenue Service labeled the tactic one of a "dirty dozen" tax scams.
The tax revelation came to light earlier in May, and Democrats continue to pepper Gomez for not releasing his tax returns.
Meanwhile, Gomez's campaign and its Republican allies have latched onto Markey's absence record from Congress, alleging the longtime U.S. congressman owes voters for the days he's missed while on the campaign trail.
Using his congressional salary, Republicans calculate Markey owes taxpayers $7,150 for missing roll call votes in the House.
"Hardworking families have to play by the rules and go to work, why shouldn't Ed Markey?" asked Massachusetts GOP Executive Director Nate Little. "While Ed hasn't had a real job for nearly four decades, the least he could do is pay the people of Massachusetts back for the time he missed this month."
Markey's campaign said the candidate was "focused on sharing the clear differences between himself and Gabriel Gomez" in the final month of the campaign.
"Over the past week and a half Ed Markey has held roughly 30 campaign or official events and meetings such as meeting with mayors from across the state, hearing from ministers in Dorchester and campaigning with Massachusetts workers in the AFL-CIO," Zucker said. "With regard to Gabriel Gomez's false attack on Ed Markey's attendance, Ed Markey is proud of his 96 percent lifetime voting record in Congress."