In response to anger from the Left, Sen. Elizabeth Warren, D-Mass., on Wednesday defended her vote to advance Ben Carson's nomination to head the Department of Housing and Urban Development, explaining on her Facebook page that Carson gave her "written promises" regarding the issues she cares about.

"Can we count on Dr. Carson to keep those promises? I don't know. People are right to be skeptical; I am," the Massachusetts senator wrote. "But a man who makes written promises gives us a toehold on accountability."

Warren wrote her note after receiving numerous criticisms on social media about the unanimous vote in the Senate Banking Committee to advance Carson's nomination to the full Senate.

Under President Barack Obama, Warren demonstrated a willingness to oppose presidential nominees. In one high-profile fight, she successfully led opposition to Obama's selection of an investment banker to serve in the number three spot at the Treasury.

Yet she voted for Carson despite what she on Wednesday called "serious, deep, profound concerns" about his experience.

She pledged that she would be the first to criticize Carson if he didn't live up to his promises to her.

For Warren, explaining herself to liberal critics is an unusual position. In the late stages of Obama's tenure, she established herself as the leader of the progressive wing of congressional Democrats, a role that she has maintained in the early days of President Trump's administration.