Credo Action is hoping to "put pressure on powerful Democrats with White House ambitions."
Federal prosecutors are firing back at the Democratic senator's legal team.
The administration is reportedly blocking a Pentagon risk assessment.
She's the 28th Senate Democrat to support the agreement.
They said the conviction demonstrates Putin's "complete disregard for international law."
Sen. Pat Roberts vowed to "use all tools of the Senate" to keep terrorists out of Kansas.
Most of the party's Senate hopefuls have yet to say whether they back Obama.
He said the agreement "will set a terrible precedent for the future."
Citizens for a Nuclear Free Iran launched a nationwide ad.
McCaskill said it would be "more dangerous" to reject the agreement.