U.S. Sen. John McCain visited Boston Monday to stump and fundraise for fellow Navy veteran and Republican Senate candidate Gabriel Gomez, who ramped up his attacks on opponent U.S. Rep. Edward Markey for voting against resolutions in Congress honoring the victims of the 9/11 terrorist attacks.

Appearing at a Dorchester VFW post before headlining a downtown Boston fundraising lunch, McCain called Gomez "the next generation of leadership in this country" and said Gomez could be counted on to support comprehensive immigration reform and to help end the pattern of sexual abuse in the military.

The appearance by McCain gave the Massachusetts Democratic Party an opening to link Gomez to the national Republican Party, a prevalent campaign tactic for candidates running in the heavily Democrat-leaning state.

Gomez, a former Navy SEAL, told the few dozen supporters assembled at the Boston Police VFW Post 1018 that it was an "honor" to welcome McCain to Boston, before criticizing Markey for voting against the resolutions in Congress in 2004 and 2006.

"To me, it's just unconscionable to have voted against something like that," Gomez said.

Gomez also critiqued Markey for voting for the Patriot Act in 2001, but later voting against reauthorizations of the bill that granted expanded investigatory powers for homeland security.

"I'm sure he's going to have some slick lawyerly explanation to try to explain votes on these matters but the bottom line is he didn't do a single thing to make sure that we were safer as a country," Gomez said.

Markey's campaign called Gomez's line of attack "despicable" and misleading, suggesting the criticisms have been "widely discredited in the past, and denounced by Democrats, Republicans and families of 9/11 victims who deserve better than for their memories to be exploited for partisan political gain."

Markey was one of 16 representatives to vote against the 2004 resolutions, and one of 22 to vote against the 2006 resolution.

"Ed Markey has always supported the victims of 9/11 - that's why he joined Democrats and Republicans like Ron Paul in voting against resolutions that blatantly politicized 9/11 and denigrated the memory of those who died. Gabriel Gomez should be ashamed of himself. For this despicable attack he owes the people of Massachusetts and victims of 9/11 an immediate apology," said campaign spokesman Andrew Zucker, in a statement.

The Markey campaign said the Congressman has voted in favor of resolutions honoring the victims of the terrorist attack eight times, but voted against the resolutions in question because Republicans inserted language praising passage of the Patriot Act and House approved immigration bill called anti-immigrant by critics.

Gomez and McCain appeared before the small crowd Monday morning before traveling to downtown Boston for a fundraiser at the Fairmont Copley Hotel. Gomez noted that he was just 2 years old when McCain's Navy plan was shot down over Vietnam, not long after his parents emigrated from Colombia. He said only in America could the son of immigrants follow in McCain's footsteps and graduate from the Naval Academy.

McCain said the special election, likely to be marked by low voter turnout in late June, will come down to get-out-the-vote efforts. "I'll be counting on our veterans," McCain said.

The senator from Arizona also suggested Gomez would be a voice of bipartisanship in Washington, before slipping up and referring to the candidate as "Gabriel Giffords," an amalgam of Gomez's name and former Democratic Congresswoman Gabrielle Giffords, of Arizona, who was shot in the head in a parking lot while meeting with constituents.

Gifford's shooting in 2011 proved to be a jumping off point for the national debate on gun control that picked up steam after the massacre at Sandy Hook Elementary School in Newtown, Conn. Markey recently launched one of the first critical television advertisements of the general election campaign, attacking Gomez for his opposition to a federal assault weapons and high-capacity magazine ban, linking the issue to Newtown.

Gomez opposes a universal background check, supports closing the so-called gun show loophole and "tying it to mental health" and has pushed back against Markey for "politicizing" the tragedy.

Gomez also steered clear on Monday of his call for term limits on members of Congress, a frequent campaign theme for the newcomer to politics running against a 36-year veteran of the House who he has called a "poster-boy for term limits." Gomez has called for a federal limit of two terms for new senators and three terms for House members. McCain is serving his fifth term in the Senate, first elected in 1986.

Three weeks into the general election campaign between Markey and Gomez, a series of polls have shown the race to be within single digits. The two have not yet debated, but Gomez has challenged Markey to three debates and over the weekend Markey said he had accepted an invitation from WBZ and the Boston Globe to debate on June 5.

After a heavy, early focus on whether Gomez would sign a pledge pushed by Markey to limit outside spending in the race, much the back-and-forth in recent days has centered on press reports related to Gomez's Cohasset home and steps he took to lower his taxable income by gifting an historic easement on the façade of his house to a charitable organization.

Cohasset bylaws already protect the home and limit the scope of work the Gomez's can do to alter the façade, and the Internal Revenue Service has called the section of the tax code allowing the deduction a "scam." Gomez, however, has insisted he followed the law and did nothing wrong.

Gomez has challenged Markey to follow his lead and release his past years of tax returns, a step Markey did not take during his primary race against U.S. Rep. Stephen Lynch but something he has promised to do this week.

As the Republican has been traveling the state introducing himself to voters, Gomez also accused Markey last week of "hiding" from voters due to the lack of public events on his schedule.

Markey campaigned over the weekend in Worcester with U.S. Rep. James McGovern and marched in the Haitian-American Unity Parade in Mattapan. On Monday, Markey planned to meet and greet construction workers in the Longwood Medical area in Boston and tour the area's new development projects with Massachusetts Building Trades Council President Frank Callahan.