I ve changed it to The series is set in the West Wing of the White House where the Oval Office and offices of presidential senior staff are located during the etc Also I don t think presidential senior staff is capitalized It s not a proper noun Generally speaking we capitalize President when using it as a noun but not always e g Barack Obama was elected president is correct I believe But we almost never capitalize it when using it as an adjective e g presidential motorcade he spoke in a manner that was very presidential etc hence we wouldn t capitalize presidential senior staff