Rep. Denny Rehberg, a Montana Republican, condemned him in the "strongest possible terms," calling his remarks "reprehensible" and adding "there is no such thing as a 'legitimate rape."
The comments were quickly seized on by Democrats who tried to link Akin to the presumptive Republican presidential ticket, putting Romney and Paul Ryan on the defensive.
"As a woman I'm really concerned that Paul Ryan doesn't understand that rape is rape," Democratic National Committee Chairwoman Rep. Debbie Wasserman-Schultz, D-Fla., said this morning on CBS, accusing Ryan and Akin of teaming up last year to pass legislation that would redefine rape.
"It is beyond comprehension that someone can be so ignorant about the emotional and physical trauma brought on by rape," Sen. Claire McCaskill,D- Mo., the Missouri incumbent who is fighting for her reelection said in a statement. "The ideas that Todd Akin has expressed about the serious crime of rape and the impact on its victims are offensive."
Additional reporting by ABC News' Emily Friedman, Shushannah Walshe, Devin Dwyer and Sunlen Miller