Paul Elliott Singer (born August 22, 1944) is an American hedge fund manager, activist investor, and philanthropist.
 His hedge fund, Elliott Management Corporation (EMC)—specializes in distressed debt acquisitions.
 Singer is also the founder and CEO of NML Capital Limited, a Cayman Islands-based offshore unit of Elliott Management Corporation.
 In 2017, "Forbes" rated Singer's net worth as $2.9 billion.
John Overdeck is an American hedge fund manager and philanthropist.
 Overdeck is the co-founder and co-chairman of Two Sigma Investments, a New York City-based hedge fund that uses a variety of technological methods, including artificial intelligence, machine learning, and distributed computing, for its trading strategies.
 In 2016, Overdeck reported $375 million in earnings and as of May 2017, Two Sigma Investments has $41 billion in assets under management.
David E. Goel (born 1970) is an American hedge fund manager.
 Goel is the managing general partner of Matrix Capital Management, which he co-founded with pioneering investor Paul Ferri in 1999.
 Goel is also a protégé of hedge fund manager Julian Robertson.
William O. Perkins III (born c. 1969) is an American hedge fund manager, film producer, and amateur poker player from Houston, Texas.
 Perkins focuses on venture capital and energy markets.
 He founded Small Ventures USA, L.P in 1997 and later joined Centaurus Energy in 2002.
 He currently manages Houston-based energy hedge fund, Skylar Capital.
Eric Mindich (born 1967) is an American hedge fund manager and the Chief Executive Officer and Founder of hedge fund Eton Park Capital Management.
 Mindich graduated from Harvard, where he was a member of the Phoenix S.K. Club, in 1988 with a B.A. in economics.
Anthony R. Chiasson (born August 27, 1973) is an American hedge fund manager and co-founder of Level Global Investors LP, a Greenwich, Connecticut-based hedge fund management firm.
 Level Global was launched in 2003 with about $500 million in assets under management and grew to $4.2 billion in assets and 75 employees before closing in early 2011.
Barry S. Rosenstein (born 1959/60) is an American hedge fund manager and activist investor.
 He is the founder of JANA Partners, a hedge fund firm.
Thomas Fahr Steyer (born June 27, 1957) is an American hedge fund manager, philanthropist, environmentalist, liberal activist, and fundraiser.
J. Kyle Bass (born September 7, 1969) is an American hedge fund manager.
 He is the founder and principal of Hayman Capital Management, L.P., a Dallas-based hedge fund focused on global event-driven opportunities.
NextGen America is an environmental advocacy nonprofit and political action committee created in 2013 by Tom Steyer supporting candidates and policies that take action against climate change.
 It has typically criticized Republican candidates, but has also targeted Democrats who have failed to take a stance on climate change.
 The organization has also been an opponent of the Keystone XL pipeline.

Question: What American hedge fund manager started the NextGen America political action committee?
Answer: Tom Steyer