Zak Ringelstein says the deciding factor will be how Sen. Susan Collins votes on Brett Kavanaugh.

U.S. Senate candidate Zak Ringelstein says if he’s unsuccessful in his long-shot bid to unseat Sen. Angus King this November, he’ll likely challenge Susan Collins in 2020.

In an interview Monday, Ringelstein said Collins’ vote on Supreme Court nominee Brett Kavanaugh will be the deciding factor.

“This is a lifetime appointment and if she doesn’t reject him, I’ll make it my personal mission to make sure she’s not elected in 2020,” said Ringelstein, 32, a former educator and entrepreneur who lives in Yarmouth.

Collins, a Republican in her fourth term, has been watched closely during the confirmation process involving Kavanaugh, President Trump’s nominee to succeed outgoing Justice Anthony Kennedy. Her vote could well be the deciding one since Republicans hold such a narrow majority.

Collins has not revealed how she plans to vote but said late last week she’s looking forward to hearing from Kavanaugh again, and from Christine Blasey Ford, the California professor who has accused Kavanaugh of trying to sexually assault her when they were both teenagers.

Ringelstein, a Democrat endorsed by the Democratic Socialists of America, said he’s still running to win against King, but is looking ahead as well.

There hasn’t been much public polling in the Senate race, but King, an independent and former two-term governor, holds a commanding lead over Republican Eric Brakey, with Ringelstein running a distant third.

Ringelstein has rejected corporate donations and has run a grassroots campaign built on a message of getting money out of politics. The only other candidate who has expressed an interest in running against Collins is Cathleen London, a physician from Milbridge.

Zak Ringelstein, 32, at right, greets Jason Hoffman of Florida and Anita Perkins of Atkinson at the Skowhegan State Fair. Ringelstein hopes to capitalize on the energy stirred up by young politicians like Alexandria Ocasio-Cortez of New York. (Ben McCanna/Portland Press Herald)