The Boston Teachers Union is supporting state Sen. Sonia Chang-Diaz’s challenger.

Hassan Williams, a Roxbury Democrat mounting a challenge to the first term senator, touted the endorsement in a release this week. Like Chang-Diaz, Williams, who has a law degree from Boston College, has worked in Boston schools.

“Mr. Williams has demonstrated his commitment to our children, to public education and to the Boston Public Schools,” said Richard Stutman, head of the union, in a statement. “His educational, financial and legal background provide him with unique and much-needed insights on educational reform, policy, the building of school partnerships as well as the importance of equitable, educational opportunities for all children. Hassan Williams’ insights, perspectives, skills and unwavering commitment to public education will be invaluable assets in the State Senate.”

Chang-Diaz, who won the Second Suffolk District seat from former state Sen. Dianne Wilkerson, is among the incumbents the teachers’ union is deciding not to endorse, leading to speculation among some that it’s a form of payback for her vote in favor of an education reform bill earlier this year. Critics of the reform say it infringes on collective bargaining rights that unions hold dear.

The Democratic primary, which will likely decide the winner, is scheduled for September 14.

The union, currently in negotiations with the city over a new contract, is also supporting East Boston High School teacher Barry Lawton in the race to replace former state Rep. Marie St. Fleur.

They also endorsed Karen Payne, the head of the local NAACP chapter, in the race to replace retiring state Rep. Willie Mae Allen in Mattapan.

West Roxbury councillor headed for Northeastern University

In a City Hall shake-up, City Councillor John Tobin announced he’s decamping for Northeastern University. Starting next month, Tobin, a West Roxbury Democrat, will be taking a job as the university’s vice president for city and community affairs.

City Hall observers are preparing to cross his name off the lengthy list of potential mayoral contenders in 2013. He was widely expected to run.

His pending departure comes a week after former City Councillor At-Large Sam Yoon, who like Tobin was one of the younger members on the council, said he was heading to Washington D.C. after his unsuccessful mayoral bid last year.

Tobin, whose family hails from Dorchester’s Lower Mills neighborhood, grew up in West Roxbury, went to UMass-Boston and has served on the council since 2002. One of the 13-member council’s more independent voices, he is the chair of the Arts and Tourism Committee.

Matt O’Malley, who has twice run for City Council, has already thrown his hat into the special election and garnered the endorsement of Sheriff Andrea Cabral, a former employer, and City Councillor At-Large John Connolly.

Proposal to tweak BPL board passes

The City Council last week unanimously passed a bill to expand the membership of the board of library trustees by four members and hand them fundraising powers.

At the state level, Gov. Deval Patrick signed off on an amendment to the fiscal 2011 budget that prevents $2 million from flowing to the Boston Public Library if any of the four libraries that are slated for closure shutter their doors. In a separate, supplemental budget amendment, Patrick also proposed “pro-rating” the cut – which library officials argue will lead to “draconian cuts” to a system already beleaguered by cuts from the state – for as long as the libraries are kept open.

The City Council’s bill, known as a home rule petition, still needs the sign-off of the mayor, the state Legislature and the governor. It was sponsored by City Councillors Michael Ross, Ayanna Pressley, and Felix Arroyo.

But it also has the support of the head of the nine-member board, attorney Jeffrey Rudman.

In a letter to Ross, Rudman said he could not speak for the board, but the bill had his support. City councillors, including Arroyo, said they were shocked to learn at a hearing on the Boston Public Library’s budget that the trustees did not fundraise.

But Councillors John Connolly and Bill Linehan said that while they supported the measure, they had also reservations about rushing the proposal through the council without a hearing. Connolly added that the fundraising ability might lead to conflicts of interests.

According to Ross, the state Ethics Commission has okayed the proposal.

Four libraries, while granted a nine-month reprieve, remain on the chopping block, including the Lower Mills branch.

The proposal to expand the board must pass the Legislature by the end of July, when lawmakers adjourn for the summer and turn their to November elections. Bills that do not make it to the governor’s desk must be re-filed in January.

Councillors say they expect Mayor Thomas Menino to sign the proposal.

Quote of Note: U.S. Sen. John Kerry on Red Sox player Kevin Youkilis

“[Yankees outfielder Nick] Swisher’s having a fine year, but Youk is better in just about every category, batting average, slugging, homeruns, everything and he plays Gold Glove defense to boot. Please don’t let anyone say that Swisher beat Youkilis because Sox fans have gone a little soft after ‘04 and ‘07. Let’s show we’re still the most ravenous fans in baseball.”

Hours after Kerry’s office sent out the email to his supporters, urging them to support Youkilis in All-Star balloting, Youkilis surged to a lead over Swisher. Unfortunately, hours after that, Youkilis left a Sox game against the Tampa Bay Rays with right ankle pain.

Balloting ends at 4 p.m. Thursday. The All-Star Game is set for July 14 in Anaheim, California.

EDITOR’S NOTE: Material from State House News Service was used in this report. Check out updates to Boston’s political scene at The Lit Drop, located at dotnews.com/litdrop.