New York ? From late-night comedy shows to cable news interviews, free media exposure has proved influential in defining the Republican presidential candidates and setting the dynamics of the primary race, especially for lower-tier hopefuls lacking cash for TV ads.

The turn toward free media, and Twitter, too, may have come at the expense of traditional campaigning. It also raises the chances that a moment of fuzzy thinking or a verbal gaffe will haunt a candidate endlessly in the YouTube world.

“The campaigns are using free media as an amplifier and it’s smart, especially for those who don’t have much money,” American University political communications professor Leonard Steinhorn says. “But there’s also a reality show quality to it all, with the kind of visual moments people don’t forget.”

There have been many such moments.

During one debate, Texas Gov. Rick Perry couldn’t remember the third of three agencies he wants to eliminate as president. A video of a Wisconsin newspaper editorial board session showed Herman Cain struggling to answer questions about Libya; the display of unpreparedness helped speed his exit from the race.

Fox factor

Fox News, long popular with conservative viewers, has been a go-to venue for the candidates.

Six contenders attended a Fox News forum hosted by Mike Huckabee last weekend in which they were questioned by three Republican state attorneys general.

Cain made regular appearances on Fox to defend himself against allegations of sexual impropriety; his wife, Gloria, did her sole campaign interview with Fox.

The network hasn’t always been friendly territory for candidates.

On a “Fox News Sunday” appearance last spring, moderator Chris Wallace pointedly asked Minnesota Rep. Michele Bachmann, “Are you a flake?” He later apologized.

Former Massachusetts Gov. Mitt Romney was panned for his performance last week in an interview with Fox News anchor Bret Baier.

Romney appeared agitated and angry when Baier pressed him on contradictory positions he’s taken on issues like abortion. “This is an unusual interview,” Romney told Baier with a forced laugh.

The regular Sunday morning shows have drawn frequent appearances from the candidates.

Romney will appear on “Fox News Sunday” on Dec. 18, his first Sunday show since March 2010.

Several candidates were booked today on the shows following the Iowa debate: Texas Rep. Ron Paul on NBC’s “Meet the Press,” Bachmann on CBS’s “Face the Nation” and Texas Gov. Rick Perry on “Fox News Sunday.”

Former Utah Gov. Jon Huntsman planned to skip the debate, but was to appear on “This Week” on ABC today.

Sunday shows, too, can be dangerous territory.

In a “Meet the Press” interview last May, Gingrich criticized a budget plan crafted by Rep. Paul Ryan, R-Wis., as “right-wing social engineering” because of its deep cuts to Medicare. He’s since apologized for the comment, but it’s become a central argument for Romney and other Republicans for why Gingrich shouldn’t be the GOP nominee.

Searching for traction, the cash-strapped lower-tier candidates have done numerous local interviews in early voting states.

Bachmann and former Pennsylvania Sen. Rick Santorum have appeared on several radio and TV shows in Iowa. Huntsman has toggled between New Hampshire and Boston shows in his quest to break through in New Hampshire’s Jan. 10 primary.

The comic approach

Several hopefuls have tried their hand with late-night comedy shows, in part to suggest they can laugh at themselves.

Huntsman yukked it up on “Saturday Night Live” last month, making fun of his low poll numbers and his fixation on New Hampshire.

“I love all of America, from Dallas, Texas, to Manchester, N.H.,” Huntsman said to laughs. “From the innovation of Silicon Valley to the affordable outlet malls in North Conway, N.H.”

Bachmann’s appearance on Jimmy Fallon’s late-night show drew controversy when the Roots, the show’s popular in-house band, welcomed her onstage with an instrumental riff from a song by the band Fishbone titled “Lyin’ Ass B—-.” Fallon apologized to Bachmann, and the band was reprimanded.

Perry visited David Letterman’s “Late Show” in an effort to recover from his infamous debate gaffe. He delivered the show’s famed “Top Ten List,” this one titled “Rick Perry Excuses.”

They included: “You try concentrating with Mitt Romney smiling at you. That is one handsome dude.”