WASHINGTON (CNN) – Freshman Missouri Sen. Claire McCaskill will endorse Sen. Barack Obama's presidential bid Sunday morning, according to her spokeswomen Adrianne Marsh.
McCaskill, who considers herself a moderate, won a very tight race in 2006 against incumbent Sen. Jim Talent, helping Democrats take control of the Senate.
Missouri is one of more than two dozen states to hold its presidential primaries February 5.
UPDATE: On a conference call with reporters announcing her endorsement of Obama, McCaskill said the decision between Obama and Hillary Clinton was a difficult one.
"This is not an easy decision for me. I have deep respect for Hillary Clinton," she said. "She’s a smart woman and a strong leader, but at this moment in history it is very important that we look forward with optimism and hope that we’ve not been able to gin up in this country for awhile.”
– CNN Congressional Producer Ted Barrett