The emerging top challenger to hard-line President Mahmoud Ahmadinejad in Iran's June elections rose up through the ranks as a solid believer in the country's Islamic revolution. Now he's the biggest hope for Iran's reform movement. Mir Hossein Mousavi's hard-line past and spotless revolutionary credentials appeal to conservatives. But his current reformist agenda and frequent clashes with the clerical establishment are believed likely to draw young voters eager for change. Mousavi, 67, came to prominence after the 1979 Islamic Revolution that toppled the US-backed shah and installed a cleric-led government. His fervor was strong enough that he was named editor-in-chief of Jomhuri-e-Eslami newspaper, then the government's main mouthpiece, used to spread its ideas in the revolution's early days. He served briefly as foreign minister, then was prime minister from 1981-1989. His premiership spanned the destructive eight-year war with Iraq, in which at least a million people on both sides were killed. Amid the widespread sacrifices at home, Mousavi ensured the war-dominated budgets included funds to provide basic goods for Iranians - and many still remember him with respect for it. The father of the Iranian revolution, Ayatollah Ruhollah Khomeini, praised Mousavi's management. As prime minister, Mousavi often clashed with the president at the time, Ayatollah Ali Khamenei - now Iran's supreme leader - over political authority. The prime minister post was eliminated after Mousavi's term, and he became known as a reformer. When reformist cleric Mohammad Khatami was elected president in 1997, Mousavi became his senior adviser. Mousavi kept a low profile, rarely speaking to the press. But his role was strong enough that reformists asked him to run for president when Khatami's two terms ended. Mousavi refused, and Ahmadinejad won the 2005 vote - a victory some blame on Mousavi's refusal. A professional architect and amateur artist, Mousavi heads the Iranian Academy of Arts that advises the government on some cultural issues. He and his wife, Zahra Rahnavard, a former chancellor of Al-Zahra University in Teheran, have three children.