Hope Su Tseng-chang (; born 28 July 1947) is a Taiwanese politician who served as premier of the Republic of China (Taiwan) from 2006 to 2007 and again from 2019 to 2023. He was the chairman of the Democratic Progressive Party in 2005 and from 2012 to 2014. Su served as Chief of Staff to President Chen Shui-bian in 2004. He is currently the longest-serving Democratic Progressive premier in history. Su actively campaigned for the DPP presidential nomination in 2008, but finished second to Frank Hsieh. Su eventually teamed with Hsieh as the vice presidential nominee; the DPP lost to the Kuomintang ticket of Ma Ying-jeou and Vincent Siew. Su ran for Taipei City Mayor in November 2010, but lost to the incumbent Hau Lung-pin by a 12-point margin. Su campaigned for the 2012 presidential candidacy of the DPP in 2011, but lost to Tsai Ing-wen by a very narrow margin. Following the loss of Tsai to Ma Ying-jeou, Su was elected to succeed Tsai as DPP chairman in 2012. During the Chen administration, Su, along with politicians Annette Lu, Frank Hsieh and Yu Shyi-kun, are collectively known as the "Big Four of the Democratic Progressive Party". Su is nicknamed the "Lightbulb" or "E Ball" () and "Go Go Go" (衝衝衝) by the Taiwanese media and DPP voters, a nickname he earned in the 1980s for his charismatic approach to campaigning during election season, in addition to being an affectionate reference to the balding Su. Personal background Su was born at Ministry of Health and Welfare Pingtung Hospital in Pingtung, Taiwan on 28 July 1947. He studied at the National Taiwan University. He was a practicing lawyer from 1973 to 1983 and became a defense lawyer in the Kaohsiung Incident trials. In September 1986, Su and seventeen others founded the Democratic Progressive Party. He was previously the magistrate of Pingtung County (1989–1993) and magistrate of Taipei County (1997–2004). His first election as the Taipei magistrate was aided by a split between the New Party, the Kuomintang, and independent candidate Lin Chih-chia. He won the election in dramatic fashion partly due to the appearance of the terminally ill Lu Hsiu-yi, who kneeled on stage in support of Su on the eve of the election. Su's subsequent reelection occurred by a wide margin despite the ability of the Pan-Blue Coalition to present a united candidate, Wang Chien-shien. He was Secretary-General (Chief of