Billionaire environmental activist Tom Steyer announced Thursday he will not run for Senator Barbara Boxer's Senate seat in 2016, saying he will be more influential in national politics from his home state California.
Steyer, who spent over $70 million in the 2014 midterm elections to boost candidates supporting climate change action, had mulled a run for the seat Boxer has held since 1993 after she decided not to run for re-election in 2016.
Steyer said the decision was "very hard" but said he will "redouble my efforts" to push for justice on climate change, economic and educational equality.
"My decision about whether to engage from the outside or seek elected office came down to a single question: How best can I fight for a level playing field at this point?" he said in a statement published in the Huffington Post Thursday.
He said the "imperative" of electing a Democratic president in 2016 along with his passion for California made him decide to stay in the state and work in states around the country "where we can make a difference."
Steyer and his PAC, NextGen Climate, supported Senate races in four states and three governors' races where the Democratic candidate took a strong position on climate change action. Three of the seven candidates won.
Steyer and his group have also been outspoken opponents of the Keystone XL pipeline, which is the focus of an intense Congressional debate taking place this week.
California Attorney General Kamala Harris declared she will run for Boxer's seat earlier this month.
She faces a potential challenge from former Los Angeles Mayor Antonio Villaraigosa and Representative Lorretta Sanchez.