The embattled chairman of the government agency that regulates America's securities industry resigned under pressure Tuesday evening. Only the timing of Harvey Pitt's resignation was a surprise.

Mr. Pitt's resignation letter arrived at the White House on Election Day evening. In it Mr. Pitt said he was resigning as chairman of the Securities and Exchange Commission because turmoil surrounding his leadership of the agency had made his job difficult. President Bush immediately accepted the resignation.

It had been a tumultuous 15 months for the former law professor and lobbyist for the accounting industry. Mr. Pitt's resignation as the country's top securities regulator comes with markets still reeling under a spate of corporate accounting scandals that led to the bankruptcy of leading companies like Enron, Global Crossing and WorldCom. Opposition Democrats have long been seeking Mr. Pitt's resignation.

President Bush lost confidence in Mr. Pitt after the disclosure last week that the person he chose to head a panel to clean up the accounting industry was himself involved with a firm tarnished by accounting irregularities.