MA Senator Scott Brown earlier called on Akin to leave the race against Sen. Claire McCaskil, before Johnson joined in. All of this follows Akin's idiotic comments over the weekend that rape rarely results in pregnancy because doctors told him a woman's reproductive system shuts down during "legitimate rape."

Romney/Ryan have also had very strong criticism for Akin. Interestingly, one of those not calling for Akin to leave the race is McCaskil: 

“It’s not my place to decide… think the people of Missouri have to make this decision,” McCaskill said on MSNBC’s “Morning Joe,” but added that his withdrawal would be “radical” after a hotly contested three-way Republican primary which Akin won “by a comfortable margin.”

Of course, it could be she wants him to hang around so she can beat the hell out of him:

“For the state I love, I hope this is a moment for everyone who hasn’t been paying close attention. This statement is a window into Todd Akin’s mind,” she said. “I hope this is one of those gut check moments [for Missourians] when they say this is not somebody we want speaking for us on the floor of the United States Senate.”

Akin did make a feeble attempt to walk back from these comments, but it doesn't appear he's going to have a lot of friends on the right having his back on this one. At least two Republican U.S. Senators have urged him to leave a race when it would allow Democrats to essentially hold a seat unchallenged. That speaks volumes.