Jay Clayton, President Donald Trump’s nominee to head the Securities and Exchange Commission, made a promise to the Senate Banking Committee Thursday to be a tough enforcer if confirmed.

But Democratic Massachusetts Senator Elizabeth Warren said he can’t keep it.

“There is zero room for bad actors in our capital markets. I’m 100 percent committed to rooting out any fraud and any shady practices in our financial system, and always be vigilant to ensure that the Commission is steadfast in protecting investors,” said the lawyer, who has represented some of the biggest banks and hedge funds in the country.

Warren doubted his ability to keep that commitment because of his work as an outside counsel for some financial giants, like Goldman Sachs and Barclays, and the work of his law firm Sullivan and Cromwell for many more.

She noted as chair, Clayton would have to recuse himself for two years from enforcement actions on any of the firms he or Sullivan and Cromwell represented.

With the SEC usually composed of three commissioners from the party in the White House and two from the outside party -- and with Republicans often opposed to enforcement actions -- the result could be that many sanctions won’t be implemented.

“If Trump wanted to make it hard for the SEC to go after his Wall Street friends, Clayton would be the perfect choice,” Warren said.

She added a financial firm that decided it wanted to ensure it would not be hit with an SEC sanction for two years could just hire Sullivan and Cromwell.

The senator noted President Barack Obama’s last SEC chair, Mary Jo White, had to recuse herself 48 times because she and her former law firm had represented clients that were being subjected to potential enforcement actions.

Hawaii Democratic Senator Brian Schatz said White’s recusals hurt the mission of the SEC.

“We need a strong, independent SEC chair on the frontline of enforcement, not watching from the sidelines,” said Ohio Senator Sherrod Brown, the lead Banking Committee Democrat, in support of Warren and Schatz. “We need a strong, independent SEC chair on the frontline of enforcement, not watching from the sidelines.”

In contrast, Republican senators on the panel were uniformly lauding the Trump nominee.

Both Idaho Senator Mike Crapo, current Banking Committee chair, and his immediate predecessor, Alabama’s Richard Shelby, praised Clayton as a top securities lawyer.

Crapo said the SEC’s three missions of investor protection, capital formation and efficient markets are equally important.