Even though he spent eight years in the Senate, GOP presidential hopeful Fred Thompson (Tenn.) has failed to corral significant support from his one-time colleagues on Capitol Hill — a reality his backers argue is immaterial and detractors say adds to questions about his electability.

In all, Thompson has secured the nod of four Senators and 17 House Members, fourth among the GOP contenders behind ex-Massachusetts Gov. Mitt Romney, who now has 33 Congressional backers, Sen. John McCain (Ariz.), who has 29, and former New York Mayor Rudy Giuliani, who has captured 24. Most of Thompson’s endorsements came weeks ago.

By themselves, Congressional endorsements don’t equate to victory, but most admit that they do serve as a gauge for the level of enthusiasm for a presidential candidate. And for Thompson — whom pundits have recently started to handicap as a long shot for the GOP nomination — the numbers could be telling.

“They are agnostic about him — and you can’t win a presidential race having a lot of people agnostic about you,” one senior Republican Senate aide said of Members. “The question is whether that lack of fire for him amongst his former colleagues is something that is replicated in the public and whether this is a [microcosm] of the public.”

But if you ask Thompson’s Congressional allies, they flatly argue that House and Senate endorsements — while not irrelevant — matter little for a candidate trying to run a strong ground game in the early primary states of Iowa, New Hampshire, South Carolina and beyond.

Thompson’s supporters admit that the former Tennessee Senator hasn’t spent too much effort of late trying to win his one-time colleagues’ favor. But they also believe Thompson’s campaign will not suffer as a result.

“I don’t think endorsements matter much in this day in time,” said Sen. Lamar Alexander (R-Tenn.), who succeeded Thompson in the chamber and supports his candidacy. “Endorsements were much more important at a time when voters didn’t know the candidate. Now we know a lot more about the candidates.”

Another Tennessean, Sen. Bob Corker (R), also advised against reading much into the level of lawmaker support for the one-time Senator’s campaign. Corker said Thompson’s energy these days is devoted to shoring up votes in the early nominating states and building up enough of a foundation leading into the mega-primary day of Feb. 5 to secure the Republican nomination.

“Fred has had this unique ability his entire life to walk through doors and things just happen,” Corker said. “He’s been successful in everything he’s done.”

Still, even Thompson’s staunchest allies acknowledge that others often view prominent endorsements as a measure of a candidate’s momentum. And that support can be seen as a broader indicator of whether the party faithful views him as a winnable candidate in a crowded field with no clear frontrunner.

“Endorsements don’t make or break a candidacy,” said one veteran Senate GOP aide. “But they certainly are a barometer for the excitement that can be built behind a candidate. If you don’t have that, it’s a telltale sign that there’s not much excitement behind your candidacy.”

It certainly appears that other Republican 2008 hopefuls think so.

As recently as last week, for instance, McCain secured the backing of conservative Sen. Sam Brownback (R-Kan.), who himself had his sights on 2008, while Giuliani won over moderate GOP Sen. Norm Coleman (Minn.). Brownback’s support for McCain was designed to show the Arizona Republican — who has fallen behind in the polls — can curry favor with conservatives.

But Rep. Adam Putnam (Fla.), the GOP Conference chairman and another Thompson supporter, said those exceptions notwithstanding, he believes “endorsements have pretty well wrapped up.”

“Here we are, two months out from Iowa,” Putnam said. “The presidential candidates ought to be a lot more focused on Des Moines than D.C. That should be where his campaign is focused. That’s where my energy would be focused.”

Indeed, Thompson has been investing his resources there, beginning a major television surge in Iowa last week, and keeping focus on the South — where a Tennessean is likely to have a head start over his northern GOP rivals. And while Thompson ranks second on average in most national surveys, he is in fourth place in the first caucus state of Iowa, fifth in New Hampshire and third in South Carolina, according to RealClearPolitics poll averages.

But those numbers aren’t discouraging to Thompson’s Congressional allies, many of whom argued last week that he’s just beginning to gain campaign steam. Thompson entered the race on Sept. 5, months after deliberating over the bid, and long after the now-frontrunners entered the hunt.

“I love his position,” Rep. Zach Wamp (R-Tenn.) said. “If you look at his favorable ratings versus his unfavorable, he is comfortable. He is setting his stride.”

Asked whether Thompson’s lack of recent Congressional support translates into a lack of enthusiasm for the candidate, Wamp responded: “Congress is in such low esteem, you don’t really want the support of Congress.”

Thompson spent the bulk of the past six years working as an actor on the hit television series Law & Order. That media presence, coupled with his conservative credentials and solid campaign resources will translate into a victory, his House and Senate backers said.

One ally said Thompson’s debate presence is ever-improving, his organization is coming together and his “road show is getting better.” This Republican said that while endorsements are “nice” and certainly “not irrelevant,” they aren’t going to do much to advance his candidacy in the early primary contests.

“Not to minimize the role of a Senator, but it doesn’t necessarily carry much weight in Iowa,” this Thompson devotee said.

Alexander agreed, arguing that he believes even though Thompson entered the race late and has trailed in some of the early states, his campaign is gaining, not losing, momentum.

“Fred always does a little better with the people than he does with the second-guessers,” Alexander said. “He runs his campaigns [with] his own style, in his own way and at his own pace.”

Thompson long has had a reputation for marching to his own beat, not only with the 2008 presidential bid, but also in his previous campaigns. In 1994 for instance, Thompson was slow to enter the Senate race but ended up mounting a historic victory over then-frontrunner Rep. Jim Cooper (D).

While in the Senate, Thompson developed a reputation as an independent Senator who never put a hefty premium on relationship-building. Several veteran Republican sources said last week that Thompson was more of a loner, sometimes seen as unapproachable and someone who never reveled in the chumminess of the chamber.

That reputation comes on top of larger questions over whether Thompson has the necessary drive to be the next president — a feeling some Republicans said could be reflected in the number of Congressional signers-on.

“His late arrival and long consideration period came across [to Senators] as being very indecisive and unenthusiastic,” said one prominent Republican lobbyist.

But just as the Johnny-come-lately play worked for Thompson in his previous political career, his Capitol Hill supporters say it will prove a successful move in the 2008 presidential race.

“We have six weeks to go,” Alexander said. “I thought it was wise. The contest is way too long and the voters will be worn out with the [other] candidates before it’s over.

“He has plenty of time.”