Claim: Gaius Baltar was portrayed by James Callis from its first appearance in "Miniseries" until his last appearance in "Daybreak (Part 3)".
Evidence: Dr. Gaius Baltar is a fictional character in the TV series Battlestar Galactica played by James Callis, a reimagining of Count Baltar from the 1978 Battlestar Galactica series. "Miniseries" "Daybreak (Part 3)" 
"Miniseries" "Daybreak (Part 3)" James Callis