Lawmakers in Olympia are taking public comment on the bill at a hearing at 3:30 p.m. Tuesday.
Democratic Rep. Steve Bergquist is the prime sponsor of the bill.
"You can affect yourself, but once you start affecting the health of others - especially kids that can't stand up for themselves - I think we need to step in and try to help out our society," he says.
Berquist tells KOMO News he took an informal poll of some third-graders recently on the issue.
"I asked what they thought of the bill, and almost unanimously they were excited that I was trying to protect them," he said.
The smoking infraction would amount to a ticket that could be as high as $250, but would not go on your driving record.
Critics of the measure, including Republican Rep. Ed Orcutt, ranking minority member on House Transportation Committee, say the government is going too far telling people they can't smoke in their own car.
"Just how far do we go with this? ... I mean, where does this end?" he said. "I do think government has reached plenty into people's lives, and to the point where it is becoming a distraction for our law enforcement."
Several states, including Oregon, already ban smoking with kids in the car.
The House Transportation Committee holds a hearing on the bill this afternoon.