THE BIDEN ADMINISTRATION on Thursday tapped Massachusetts Transportation Secretary Stephanie Pollack as deputy administrator of the Federal Highway Administration, creating a yawning void in the state’s transportation bureaucracy.

Gov. Charlie Baker announced that Jamey Tesler, who currently runs the Registry of Motor Vehicles, will serve as acting secretary once Pollack steps down on Tuesday.

The appointment of Pollack to the federal highway administrator’s job is another step in her evolution. She started out as a left-leaning, pro-tax, transit advocate working at the Conservation Law Foundation and Northeastern University’s Dukakis Center for Urban and Regional Policy; moved on to be a fierce advocate for her Republican boss’s cautious, no-tax transportation policies; and now is headed to Washington to deal with highway issues.

Often described as the smartest person in whatever room she is in, Pollack demonstrated a strong command of just about every facet of state transportation. Where she struggled at times was trying to bridge the gap between the strong desire among transportation advocates and many on Beacon Hill to rapidly modernize the state’s transit system and her boss’s desire to do so on a much slower timetable.

James Aloisi, a former secretary of transportation himself who current serves on the TransitMatters board, called Pollack’s appointment in 2015 “a solid and stunning choice.” In an interview on Thursday, he said his high expectations back then came down to earth as he came to realize that Pollack viewed her job as working for and carrying out the policies of the governor. He said her approach was understandable, and helps explain why she held on to the secretary’s post for six years, longer than her three predecessors combined.

“She was very transparent from the get-go. She has been a highly effective lawyer/advocate for her client’s position,” he said, referring to Baker.

But Aloisi described her tenure as “a missed opportunity,” citing her inaction on some of the biggest transportation issues facing the state – the Allston I-90 interchange, a Red-to-Blue line connector on the subway system, and her failure to push for swift electrification of the commuter rail system.

Pollack is a tireless administrator, but the constant fighting between transportation advocates and the Baker administration over the last several years appeared to take its toll. “I have the sense that she hasn’t been happy in the job for awhile,” Aloisi said.

At a State House press conference, Baker praised Pollack, calling her “a terrific performer” who will be great asset to the Biden administration. “It’s a bummer for us, but we do now have somebody in Washington who really understands what we’re about,” suggesting that familiarity might help the state as it tries to secure federal funding.

Tesler brings vast experience to his new job, having served as chief operating officer, chief of staff, and assistant secretary for procurement for the Massachusetts Department of Transportation. He has also held jobs at the MBTA, the state treasurer’s office, and in the legal office of former governor Jane Swift.

Pollack tapped Tesler as registrar of motor vehicles in 2019 when that agency was engulfed in controversy after a truck driver impaired by multiple drugs mowed down seven motorcyclists in New Hampshire. It was subsequently discovered that the driver should have had his license suspended by the Registry of Motor Vehicles after he had his driving privileges revoked in another state, but the agency failed to act on the notice it received about the earlier driving infraction.

Aloisi said Tesler was his top deputy when he was secretary of transportation under Deval Patrick. “He was the person I went to for advice three or four times a day,” Aloisi said. He called Tesler a terrific choice and said the secretary’s job is in good hands.

Tesler faces a huge decision over the next several months on the I-90 Allston interchange project. The city of Boston and most transportation advocates have urged Pollack to rebuild at grade level a crumbling elevated section of the Turnpike and other transportation infrastructure between Boston University and the Charles River, straighten the Turnpike in that area, and build a new commuter rail station to make way for a new neighborhood being built by Harvard University.

After years of research, Pollack has failed to make a decision on what construction approach to follow. In recent months, she has said money for the project is scarce and suggested she may end up patching the crumbling elevated section of the Turnpike and do none of the other elements of the project. Her new Washington job may give her the ability to free up some funding for the project.

Rep. William Straus of Mattapoisett, who has been the House’s point person on transportation issues, said the Allston I-90 interchange project appears to be at a virtual standstill. He said the departure of Pollack and a change at the bargaining table might be helpful in moving the project along.

“Whether she intended it or not, Stephanie Pollack has become something of a lightening rod,” he said.