Wu, a Democrat, has been getting ready for her testimony before Congress for weeks. WBZ-TV has learned the mayor's office paid an outside law firm, Cahill Gordon & Reindel, $650,000 to help Wu prepare. Massachusetts has two representatives on the House Oversight Committee - Congressman Stephen Lynch and Congresswoman Ayanna Pressley.

Boston Mayor Michelle Wu is set to testify before Congress on Wednesday on the city’s immigration policies as Republicans take aim at four so-called “sanctuary cities” amid President Donald Trump’s push for mass deportations.

Wu is one of four Democratic mayors set to testify before the committee, whose GOP leadership is investigating the immigration practices of Boston, Denver, Chicago, and New York in what’s expected to be a splashy, made-for-TV hearing.