Rudy Giuliani has made his performance on Sept. 11 the dominant pillar of his campaign, a strategy that has proved at once effective and controversial. While the former New York City mayor finds himself atop national polls and well-positioned to capture the Republican nomination, he has also exposed himself to criticism that he is overstating his terrorism credentials and crassly politicizing the issue.

Yet just three months before the first primary vote is cast, none of Giuliani's top-tier primary opponents have taken the bait.

Despite privately acknowledging that there is ample ammunition to attack Giuliani for his handling of and work after 9/11, the GOP presidential frontrunners have been either too cautious or afraid to speak out. Their silence underscores a strategic calculation that Giuliani's 9/11 record will be picked apart by Democrats, and other foes of Rudy; but also a fear that bringing up the terrorism issue could backfire.

"I'm not going to get into it at all because we are not willing to use 9/11 for political purposes," Jeff Sadosky, a spokesman for former senator Fred Thompson, R-TN, told the Huffington Post.

"I could go on all day about that," said Alice Stewart, a spokesperson for former governor Mike Huckabee, R-AK, before asking for time to organize her thoughts and never calling back.

To be sure, there have been multiple opportunities to go after Giuliani on his perceived strong suit. The International Association of Fire Fighters lashed the former mayor for failing to outfit first responders with modern radio equipment and prematurely ending the search for firefighters buried under the 9/11 rubble. Jerry Hauer, who once ran Mayor Giuliani's Office of Emergency Management, called the perception of Giuliani as a terrorism expert a "fabrication" and "lie."

"In the time I worked for Rudy," Hauer told the Huffington Post. "I never heard him talk about Jihadists or Jihadism or Islamic fundamentalists or Hamas, Hezbollah, or al Qaeda... The words al Qaeda never even came out of Rudy's mouth." (Read more below.)

Privately, Giuliani's Republican opponents say criticisms like these could impact the primary race. But one official from a rival campaign told the Huffington Post that the idea of going after Giuliani on these grounds hadn't even come up during a strategy session.

If they went after him, Stephen Wayne, Professor of American Government at Georgetown University, told the Huffington Post, "He would shout back about the need for strong leadership during crises, and that he was there and they weren't. Given the audience - the Republican constituency - any attempt to do that would backfire. It doesn't mean they can't attack him on 9/11, but they are going to have to do it in a way that won't trace back to them."

Not all of Giuliani's opponents have kept their silence. Rep. Ron Paul, R-TX, has repeatedly sparred with Giuliani over the root causes of terrorism during GOP presidential debates.

"I think it's interesting that [Rudy] continues to bring this up as a central point to his campaign when he doesn't really understand what happened on 9/11," Jesse Benton, a spokesperson for Paul, told the Huffington Post. "He doesn't understand the motivating factors and he doesn't understand what to do to prevent another attack." Giuliani's campaign did not return a request for comment.

And during Wednesday night's Democratic debate at Dartmouth College, Senator Joe Biden, D-DE, called Giuliani the "the most uninformed person in American foreign policy now running for president."

"It becomes obvious at a point where you are using the event rather than respecting it," Larry Rasky, Biden's communications director, told the Huffington Post. "[Giuliani] seems to have this campaign that says, because I was mayor of NYC on 9/11, I know everything there is to know about terrorism and everything in the world is related to terrorism. It is a view of the world we reject."

This past week presented another instance in which the Giuliani camp's invocation of 9/11 stirred the political pot. A fundraiser, on the mayor's behalf, put forward the suggested donation of $9.11. Democrats were quick to howl. "Unconscionable, Shameless And Sickening," declared Senator Chris Dodd, D-CT.

Yet Republicans, once again, stayed on the sidelines.

"I think about [Senator] John Edwards' comment - the war on terrorism is a bumper sticker slogan - and I think that having a fundraiser like that certainly doesn't help fight that statement," said one Republican Giuliani opponent.

Would you say that on record?

"No," he replied. "9/11 is too touchy subject, especially to attack someone on."