WASHINGTON (Reuters) - 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 here 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 President-elect Joe Biden announces a new chair after his administration takes over on January 20. 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 or contentious rulemakings to a vote while he is caretaker. Democratic SEC commissioner Allison Lee and former Democratic commissioners Kara Stein and Rob Jackson are contenders to replace Clayton, Reuters has previously reported here. Gary Gensler, an ex-chair of the Commodity Futures Trading Commission, is also a contender, as is Preet Bharara, the former U.S. Attorney in Manhattan whom Trump fired in 2017. Roisman is a former SEC and U.S. Senate lawyer. As commissioner, he has led a campaign to overhaul shareholder voting rules with the backing of congressional Republicans. Progressive Democrats, investor groups and powerful unions have opposed the changes, saying they muzzle investors and will make it harder to push corporations on climate change and social issues. Analysts expect Biden will to try to reverse them. A formal White House decision to appoint Roisman as acting chair would break with protocol. Typically, the longer-serving party commissioner, in this case Peirce, steps up. Peirce is an ultra conservative who has often broken ranks with her fellow Republicans on enforcement issues and cryptocurrency oversight.