BOSTON — State Rep. John Lawn, the longtime Watertown Democrat and chair of the powerful Health Care Financing Committee, has confessed to driving drunk and fleeing a crash just steps from the State House — in a boozy late-night disaster that’s now threatening his political career.

Lawn was arrested around 1:45 a.m. Wednesday after allegedly plowing his GMC Yukon into a parked car on Hancock Street, running multiple stop signs, and circling Beacon Hill like a man with something to hide. According to police, a concerned witness trailed the swerving SUV and flagged down an officer as Lawn finally parked on Bowdoin Street — directly across from the State House.

What officers discovered was damning: heavy damage to Lawn’s front wheel, bloodshot eyes, slurred speech, and the stench of alcohol. The arrest report says the wheel was bent at an “extreme degree not consistent with normal vehicle operations.”

Initially, a not guilty plea was entered on Lawn’s behalf during a standard Thursday morning arraignment — but hours later, the Democrat returned to court and admitted to the facts.

He will lose his license for 45 days, must attend alcohol treatment and education programs, and pay a series of fines. If he stays out of trouble for a year, the drunk driving charge will be wiped from his record. The hit-and-run charge could disappear in six months under the same deal.

Outside the courthouse, Lawn gave a short statement:

“I deeply regret my actions the other night. I take full responsibility... I feel terrible and will do all I can to make sure I live a better life and a healthier life.”

But Lawn refused to answer questions, including whether he plans to resign or explain where he was before the crash.

Lawn has served in the House since 2011 and holds sway over billions in state health care spending. His arrest now raises serious questions about accountability on Beacon Hill — and whether lawmakers who write public health policy are living by the standards they impose on everyone else.

No comment yet from House leadership.