Prominent outing blogger Mike Rogers alleges Mark Kirk is gay.

Kirk is the Illinois Republican representative who lost a critical Human Rights Campaign (HRC) endorsement after he voted against repeal of the law that bans gay troops from serving openly. The gay rights group decided to back Illinois Treasurer Alexi Giannoulias, Kirk's Democratic challenger for the Illinois Senate seat once held by President Barack Obama, after Kirk voted against attaching a “Don't Ask, Don't Tell” repeal amendment to the defense budget bill late last week. Kirk, however, did vote in favor of the $700 billion defense bill, which included the repeal amendment, one of the few House Republicans to do so.

“Mark Kirk told me he was gay,” Rogers wrote on his outing blog

Rogers says Kirk asked him about the situation of a gay man during a D.C. party in 2004.

“As my friend walked away, Kirk asked me if the man who introduced us was 'single or attached,'” Rogers said. “When I said that he had a partner Kirk replied disappointingly, 'oh, well.'”

Kirk is considered a moderate gay ally for his backing of a federal hate crimes law that includes sexual orientation and gender identity and the Employment Non-Discrimination Act (ENDA), a bill that would outlaw workplace LGBT discrimination, which is why, Rogers says, he did not out Kirk earlier.

“My thoughts then were that he wasn't THAT bad on gay stuff,” Rogers said.

But within days of Kirk's vote against repeal of DADT, Rogers said 5 men approached him with stories of Kirk's sexual orientation.

Last January, Kirk faced similar allegations by his GOP primary opponent, Andy Martin. Martin accused Kirk of being gay and, ironically, that his allegiance was owned by gay rights groups. Allegations Kirk has denied.

Recently polling puts Kirk and Giannoulias in a virtual dead heat.