Updated 10:31 a.m. | Col. Mark Kelly, the husband of retired Rep. Gabrielle Giffords (D), wrote an email Friday evening that was critical of retired Air Force Col. Martha McSally, the Republican running for the House seat formerly held by his wife.

Kelly has backed McSally’s Democratic opponent, Rep. Ron Barber, since his first run for Congress in a June special election to replace Giffords.

According to an email sent to Barber’s list of supporters, a comment McSally made to the Washington Post sparked Kelly’s ire.

“We are rugged individuals,” she told the Post. “We elect unique people to represent us in this district — Mo Udall, Jim Kolbe, Gabby Giffords. I resemble Gabby Giffords more than the man who worked for her, although I am grateful for his service.”

In an email with the subject line “I cannot believe this,” Kelly proceeded to express outrage at McSally for comparing herself to Giffords.

“Martha McSally is no Gabby Giffords.  Time and time again, she has refused to give a straight answer when asked directly about the most important issues facing Southern Arizona,” he wrote.

He called her quote “outrageous.”

Updated 10:31 a.m.

“Ron Barber’s campaign is so desperate that Martha can’t even compliment Gabby Giffords for her leadership without being viciously attacked,” McSally campaign manager Bruce Harvie responded in a written statement. “Attacking is not leadership. Ron Barber is clearly desperate and willing to say or do anything to keep his job in Washington.”

Kelly has been politically active over recent weeks and months. He has penned donor solicitations to various Democratic groups, including EMILY’s List.

McSally is widely considered the most formidable candidate Republicans have put forward in recent years to represent the Tucson-based district.