McCaskill is the first sitting member of Congress to endorse the group, called Ready for Hillary.
The organization does not have official ties to the former secretary of state but it’s trying to lay the foundation for another Clinton campaign.
McCaskill was an early supporter of Barack Obama when he was running for president in 2008. She says it’s important for supporters of Clinton to start early and build a “grassroots army from the ground up” to help the former first lady if she decides to run for president.
McCaskill was re-elected to her second term in the Senate in 2012.
Source: Associated Press