They sent a letter in June to the State Department's inspector general suggesting members of Abedin's family may have connections to the Muslim Brotherhood, which the writers said may be seeking access to high levels of the U.S. government.
Most attention has focused on Bachmann, who earlier this year failed in her bid for the Republican presidential nomination. She has long been criticized by fellow Republicans, among others, for controversial comments and factual errors.
Bachmann defended her actions Thursday on the talk show of conservative host Glenn Beck. "If my family members were associated with Hamas, a terrorist organization, that alone could be sufficient to disqualify me from getting a security clearance," Bachmann said, according to a transcript of her remarks. "So all we did is ask, did the federal government look into her family associations before she got a high level security clearance."
There is no evidence connecting Abedin or her family to any terrorist organization, McCain stressed in his Senate speech.
"Rarely do I come to the floor of this institution to discuss particular individuals," McCain said. "But I understand how painful and injurious it is when a person's character, reputation, and patriotism are attacked without concern for fact or fairness."
He called Abedin "an intelligent, upstanding, hard-working, and loyal servant of our country and our government, who has devoted countless days of her life to advancing the ideals of the nation she loves and looking after its most precious interests."
A State Department spokesman said Clinton "very much values" Abedin's "wise counsel and support" and called the allegations preposterous.