JERUSALEM — Calling herself ‘‘an answer to the contention that there is no one to vote for,’’ Tzipi Livni, Israel’s centrist former foreign minister, returned to politics Tuesday after a six-month hiatus, heading a new party that she described as ‘‘an alternative, personal and ideological,’’ to Prime Minister Benjamin Netanyahu.

‘‘I’ve come to fight for Israel,’’ Livni, 54, said in an impassioned 20-minute speech at the journalists’ union office in Tel Aviv. ‘‘I haven’t come to fight against but to fight for.’’