Fred Thompson said Friday while visiting a New Hampshire gun store that former New York City Mayor Rudy Giuliani should stop bringing up the Big Apple on the campaign trail and criticized him for consistently supporting gun control legislation.

Thompson's popularity in early-voting New Hampshire has sunk rapidly in recent weeks, but his visit to Skip's Gun and Sport Shop to trumpet second-amendment rights could be geared toward libertarian-leaning primary voters in the state.

And the usually laid-back Thompson aimed his tough talk straight at the Republican frontrunner.

"(Giuliani) simply supported just about every gun control legislation that came down the pike. And I just disagree with him on that.... over the years and he's been very outspoken about it. Of course he's not outspoken about it anymore," Thompson told reporters with a smile. "It's a major differentiation. He relates everything to New York City ... Well, New York City is not emblematic of the rest of the country.

"And the sentiments of those people in the rest of the country are in support of the second amendment. This is where I've always been ... and I don't think he's ever been," he said.

The former Tennessee senator and "Law & Order" actor consistently ranks in the top tier of presidential candidates in national polls, but his fortunes in New Hampshire, which just set its influential first-in-the-nation primary for Jan. 8, have taken a turn.

Thompson pulled only 4 percent in the latest CNN-WMUR-TV poll of 404 likely Republican voters in the Granite State. The same poll showed Giuliani with 16 percent and former Massachusetts Gov. Mitt Romney with 33 percent support. The poll, taken from Nov. 14-18, had a margin of error of 5 points.

Giuliani, who leads in most national polls, regularly turns voters' attention to his record in New York as mayor during the Sept. 11 attacks, as well as his record as a mob-busting, crime-fighting federal prosecutor. He has justified his support of gun control legislation by saying it helped reduce crime in New York.

Thompson, however, vocally disagrees with Giuliani on the issue.

"I used to have my own skeet shoot," Thompson boasted as he wandered through the gun shop and bought his children gifts. "Some of my opponents, you know, have a bad record or no records. I have a solid record. ... I'm not embarrassed to remind anybody of it."

A Giuliani spokeswoman said Thompson should be careful with his rhetoric.

"Coming from a man who lives in the Beltway, who is a Washington insider and lobbyist and who played the role Rudy Giuliani actually lived on a television series, I am not sure what to make of the senator's comments, except to say results are results," Katie Levinson said.

FOX News' Cristina Corbin and The Associated Press contributed to this report.