WASHINGTON -- Sen. John McCain (R-Ariz.) vigorously defended top State Department official Huma Abedin, who is Muslim-American, against allegations by Rep. Michele Bachmann (R-Minn.) and other conservatives that she is part of a Muslim Brotherhood conspiracy to infiltrate the U.S. government.

"These allegations about Huma and the report from which they are drawn are nothing less than an unwarranted and unfounded attack on an honorable woman, a dedicated American and a loyal public servant," McCain said in a speech on the Senate floor on Wednesday morning.

The accusations stem from a report by the Center for Security Policy. The organization is run by Frank Gaffney , who has been crusading against the rise of the Muslim Brotherhood and Sharia law for years.

Bachmann, along with Reps. Trent Franks (R-Ariz.), Louie Gohmert (R-Texas), Thomas Rooney (R-Fla.) and Lynn Westmoreland (R-Ga.), recently sent letters to five federal agencies demanding investigations into infiltration by the Muslim Brotherhood, citing Gaffney's work.

McCain never mentioned Bachmann or the other lawmakers by name, but pointedly criticized their letters and the report, noting he had worked with the Center for Security Policy in the past.

"The letter alleges that three members of Humas family are 'connected to Muslim Brotherhood operatives and/or organizations,'" he said. "Never mind that one of those individuals, Humas father, passed away two decades ago. The letter and the report offer not one instance of an action, a decision or a public position that Huma has taken while at the State Department that would lend credence to the charge that she is promoting anti-American activities within our government."

"These attacks on Huma have no logic, no basis and no merit," McCain added. "And they need to stop now."

Abedin, a longtime aide to Secretary of State Hillary Clinton, is married to former Democratic Rep. Anthony Weiner, who is Jewish and strongly pro-Israel.

McCain said that he traveled overseas with Clinton and Abedin when Clinton was a senator.

"I have every confidence in Huma's loyalty to our country, and everyone else should as well," he said. "All Americans owe Huma a debt of gratitude for her many years of superior public service. I hope these ugly and unfortunate attacks on her can be immediately brought to an end and put behind us before any further damage is done to a woman, an American, of genuine patriotism and love of country."

But McCain said his larger reason for condemning Bachmann's allegations is to stand up for the character of America.

"Ultimately, what is at stake in this matter is larger even than the reputation of one person," he said. "This is about who we are as a nation, and who we still aspire to be.

"When anyone, not least a member of Congress, launches specious and degrading attacks against fellow Americans on the basis of nothing more than fear of who they are and ignorance of what they stand for, it defames the spirit of our nation, and we all grow poorer because of it."

In a statement on Wednesday, Bachmann said that her letters were being "distorted ," but she did not directly address McCain or mention Abedin.

"I encourage everyone, including media outlets, to read them in their entirety," she said in a statement. "The intention of the letters was to outline the serious national security concerns I had and ask for answers to questions regarding the Muslim Brotherhood and other radical group's access to top Obama administration officials."

Rep. Keith Ellison (D-Minn.), who was the first Muslim-American elected to Congress, also condemned the allegations against Abedin Wednesday.

"I think it just is the worst of guilt by association ," Ellison told CNN 's Anderson Cooper . "I think it's really reprehensible and I do hope that people stand up to it."

Ellison also sent Bachmann a letter Wednesday saying that he hadn't seen any evidence supporting her claims about the Muslim Brotherhood, even after she responded to a letter he sent her on July 12 asking her to back them up.

"A careful review of your 16-page response reveals that you fail to provide any credible evidence for your claims, engage in guilt by association, and continue to rely on discredited sources," he wrote.

Ed Rollins, Bachmann's former campaign chairman, posted a blistering op-ed on Fox News' website on Wednesday afternoon, comparing her allegations to the conspiracy theories of former Sen. Joseph McCarthy:

I have been a practitioner of tough politics for many decades. There is little that amazes me and even less that shocks me. I have to say that Congresswoman Michele Bachmann's outrageous and false charges against a top aide to Secretary of State Hillary Clinton, Huma Abedin reaches that threshold.

Her unsubstantiated charge against Abedin, a widely respected top aide to Secretary Hillary Clinton, accusing her of some sort of far-fetched connection to the Muslim brotherhood, is extreme and dishonest.

Having worked for Congressman Bachman's campaign for president, I am fully aware that she sometimes has difficulty with her facts, but this is downright vicious and reaches the late Senator Joe McCarthy level.

[...]

Shame on you, Michele! You should stand on the floor of the House and apologize to Huma Abedin and to Secretary Clinton and to the millions of hard working, loyal, Muslim Americans for your wild and unsubstantiated charges. As a devoted Christian, you need to ask forgiveness for this grievous lack of judgment and reckless behavior.

Other lawmakers roundly condemned Bachmann's allegations Wednesday night and Thursday morning.

Sen. Scott Brown (R-Mass.) weighed in on Twitter , writing, "Rep. Bachmanns accusations about Sec. Clinton aide Huma Abedin are out-of-line. This kind of rhetoric has no place in our public discourse."

House Minority Leader Nancy Pelosi (D-Calif.) also took to Twitter , writing, "I applaud @SenJohnMcCain for his powerful rejection of baseless accusations against Huma Abedin + other Muslims. I wish this discourse no longer existed in our country, but we have more educating to do with respect to what America is about."

Sen. Lindsey Graham (R-S.C.) -- whom McCain specifically mentioned in his floor speech as being one of the members who traveled with Clinton and Abedin abroad -- also condemned the attacks, calling them "ridiculous, really off-base, inappropriate ."

"The person saying it has no idea what they're saying because they've never met her," he told Politico's Huddle. "She is about as far away from the Muslim Brotherhood view of women and ideology as you possibly could get. She's a very modern woman in every sense of the word, and people who say these things are really doing her a disservice because they don't know what they're talking about, and I don't know what their motivations are, but clearly it says more about them than it does her."

CNN's Dana Bash tried to catch up with Bachmann on the Hill Wednesday to ask her about the reaction to McCain's comments, but the congresswoman refused to stop and talked over Bash:

While most of Bachmann's four co-signers have stayed silent as well, Rooney said he believed the allegations were legitimate, although he regretted the focus on Abedin.

"I regret that Mrs. Abedin has become the media focus of this story, because the intention of the letters was to bring greater attention to a legitimate national security risk," Rooney said in a statement.

The Center for Security Policy issued a statement saying that McCain clearly had not fully reviewed the organization's "curriculum " and its "extensive documentation of a stealthy 'civilization jihad' being mounted against this country, its civil society institutions and government."

"Congresswoman Bachmann and her colleagues have rendered a tremendous public service by raising an alarm about the dangers posed by the Muslim Brotherhoods civilization jihad,'" Gaffney said in the statement. "Far from being chastised for doing so, by Sen. McCain or others, they should be applauded and aided in their efforts to have the extent of Brotherhood influence operations properly investigated by Inspectors General and/or congressional committees."

The organization also invited Huma Abedin's mother -- Dr. Saleha Mahmood Abedin, whom Gaffney's group accuses of supporting an organization that promotes shariah law -- to "participate in a dialogue."

The New York Times applauded McCain for speaking out in an editorial published Thursday, entitled "McCarthyism Redux ."

"Since his defeat for the White House four years ago, Senator McCain has too often seemed a listless, unpredictable political figure, forgetful of his own bearings as his party steered resolutely rightward," the editorial said. "It was heartening to hear him back on deck condemning Know-Nothingism, especially in a week that started with his vote against a campaign finance disclosure act that should have had his strong backing."

This story was updated extensively after its initial publication Wednesday afternoon with reaction from lawmakers and others.