Billionaire targets Dem on Keystone XL in Mass. Senate race

"If you can’t or won’t do either, then you’ll be showing us that you stand with Republicans and a wealthy foreign oil company and against solving the climate crisis. You’ll be standing for the wrong energy future for America," the letter reads.

Lynch campaign spokesman Conor Yunits dismissed the letter, saying in a statement that, “This letter reads like something out of a James Bond film — a billionaire making threats and issuing ultimatums that expire at ‘high noon.’”

Lynch has in the past voted to pressure President Obama into expediting approval of the proposed Canada-to-Texas pipeline. Obama has the final say because Keystone crosses national borders.

Lynch is running against Rep. Edward MarkeyEd MarkeyDems push for more action on power grid cybersecurity Dem senator: Trump 'doesn't respect' the presidency Overnight Regulation: Labor groups fear rollback of Obama worker protection rule | Trump regs czar advances in Senate | New FCC enforcement chief MORE (D-Mass.), a vocal Keystone opponent, in the Democratic primary to fill Secretary of State John KerryJohn KerryFrustrated Dems say Obama botched Russia response Budowsky: Dems madder than hell Tillerson: 'My view didn’t change' on Paris climate agreement MORE's former seat.

Markey has won endorsements from several environmental groups. He has earned praise from that community for his stances on climate change, clean energy and his oversight and criticism of the oil industry and offshore drilling.

Keystone’s backers contend it would bring jobs and oil supplies from an ally, and that it would not devastate the climate.

Opponents — largely progressive and green groups — argue it would add 35 permanent jobs, ramp up carbon emissions, and that most of the oil is intended for export.

The Hill’s Alexandra Jaffe has more on Steyer’s letter to Lynch here.