(Meredith Nierman/AP)

In a debate that reprised many of the same policy and political themes Rep. Ed Markey (D) and former Navy SEAL Gabriel Gomez (R) have tangled over for weeks, the two Senate candidates found time Tuesday night to tussle over someone who already has a spot in the upper chamber.

One lengthy exchange was dedicated to the question of whether Gomez told Sen. John McCain (R-Ariz.) that it's time for him to call it a career in the Senate.

"Mr. Gomez, you just had John McCain in campaigning for you three weeks ago. Did you ask John McCain to leave the Senate?" Markey asked Gomez, in response to the Republican questioning whether his opponent believes members of Congress should be term-limited.

"Just to be frank, I did tell Sen. John McCain that he should be term-limited," responded Gomez.

Markey shot back: "Mr. Gomez did not tell John McCain 'this should be your last term. You should just be leaving right now.' That never happened. That conversation did not happen."

McCain spokesman Brian Rogers said: "Senator McCain did discuss the issue of term limits with Gabriel Gomez when they campaigned together last month. They disagree on this particular issue, but agree on many others. Senator McCain believes that Gabriel Gomez represents the next generation of leadership that we need in the U.S. Senate."

In the final debate of the race for the seat once held by Secretary of State John F. Kerry, that was just one of many areas where the two candidates did not see eye to eye.

Markey hit Gomez over his personal taxes. "Mr. Gomez makes ten times more than I make per year and he paid pretty much the same tax rate," the Democrat said.

Gomez countered Markey's questions about his private equity work by taking issue with his opponent's terminology. "If you knew what private equity was, you'd know that we don't have clients. It's that simple. We have investors," Gomez said.

Neither candidate landed a knockout blow with just a week left in a race that has looked increasingly positive for Markey. Polls released this week show the Democrat up by between seven and 11 points. And Markey received a parade of reinforcements from national Democrats while GOP groups have largely shied away from coming in for Gomez.

As he has before, Markey hit Gomez from the left on guns, entitlements and abortion. Gomez reiterated his consistent refrain that Markey has been in Congress for too long and is afraid to stray from the party line.

Gomez made a concerted effort to separate himself from the national GOP, noting multiple issues over which he disagrees with many Republicans.

"They're wrong on immigration right now. They're wrong on gay marriage right now. They're wrong on the expanded background checks right now. They're wrong on the environment on global warming right now. I'm on the right side of that," said Gomez, who promised to work with Democrats.

Markey, who noted throughout the evening that Gomez has received support from the likes of Senate Minority Leader Mitch McConnell (R-Ky.) and other well-known Republicans, said Gomez was a champion of the "oldest and stalest Republican ideas."

On the national security front, both candidates agreed that Edward Snowden, the man who revealed details of the government's sweeping surveillance efforts to The Washington Post and Britain's Guardian newspaper, should be prosecuted. Markey stopped short of calling him a "traitor." Gomez said that if he "put anybody's life in danger, he is absolutely a traitor."

Gomez closed by asking for voters for "17 months" to see if he has kept his word about the platform on which he is running.

Markey got the last word at the debate, which took place at the studio of WGBH-TV. He said he is running "to go down to Washington to protect a more fair society, to ensure that every American, regardless of income or race can maximize all of their human ability."