WASHINGTON—U.S. Securities and Exchange Commission (SEC) Republican Commissioner Hester Peirce on Thursday tweeted congratulations to her Republican counterpart at the agency Elad Roisman, who would serve as the acting agency head after Jay Clayton announced he was stepping down on Wednesday. “Congratulations, Chairman Roisman!, I look forward to your leadership of the SEC.” Roisman, the SEC and the White House did not immediately respond to requests for comment. Roisman, who has been a commissioner since 2018, would run the agency which oversees public companies, brokers, Wall Street banks, and investment funds, until a new chair is selected. Clayton, a former Wall Street lawyer, was appointed by President Donald Trump in 2017. His departure leaves the SEC, which is led by political appointees who vote on rules and other key issues, tied at two Republican and two Democratic commissioners. That makes it unlikely Roisman will be able to bring any substantial …