Original: Following the resignation of Gordon Brown as Prime Minister and Labor Leader , Harman became Party Leader and replaced Conservative Party Leader David Cameron ( who became Prime Minister ) as Leader of the Opposition . She served in both roles until the Labor party elected Ed Miliband as Leader .
Simplified: Following Brown 's resignation as Labor leader on 10 May 2010 , Harman was the acting leader of the Labor Party until Ed Miliband was elected on September 25 , 2010 .