 Complete the following phrase:  From June 2002 until January 2005, Medvedchuk served as head of President Leonid Kuchmas presidential administration. As such, he was a leading target for criticism by the opposition, including Viktor Yushchenko who often spoke out bitterly against Medvedchuk. Medvedchuk was considered the main behind-the-scenes man of then-Prime Minister and pro-Kuchma presidential candidate Viktor Yanukovych in the 