。
Koizumi has already entered safe territory in the election.
Literal
Election [at-で] Koizumi-[formal-suffix-氏] [topic-は] already safe-zone [into-に] entered.
Political news reporting. The suffix ~氏 after a name is a formal/journalistic honorific for public figures, especially men — more neutral than ~さん and typical of newspaper and broadcast prose. 安全圏 ('safe zone') is used figuratively here for 'a position where victory is assured.' 選挙で uses で for the activity-location of being in an election.