William Donaldson is no fan of Regulation Fair Disclosure, the securities regulation that's supposed to level the playing field between Wall Street pros and Main Street investors by giving them equal access to market-moving information. But don't expect him to move to overturn the rule if he's confirmed as chairman of the Securities and Exchange Commission. People who know Donaldson, 71, who was nominated Tuesday by President Bush, say such a radical move would be inconsistent with the management style he's displayed through his long career on Wall Street. Donaldson's main objectives are more likely to center on bringing stability to the SEC, they say, especially after the brief but stormy reign of outgoing SEC Chairman Harvey Pitt. Indeed, most Wall Street observers say Donaldson will have so much on his plate when he takes over the SEC that the idea of taking another look at Regulation FD probably won't be a high priority. The 2-year-old regulation was the crowning achievement of former SEC Chairman Arthur Levitt during the Clinton administration. The controversial rule, which many on Wall Street opposed, prohibits corporate executives from providing Wall Street analysts and institutional investors with a heads-up on potential market-moving information. Levitt and investor advocates argued the rule was needed to make it more difficult for Wall Street firms and institutional traders to buy and sell shares of a stock before a major corporate announcement was released to the general investing public. Critics like Donaldson, meanwhile, said the regulation would force corporate executives to stop talking to analysts and result in all investors getting less guidance about future earnings. But securities experts say it would be pretty much unprecedented for an SEC chairman to come in and try to overturn a regulation he didn't like, even one with a long Wall Street pedigree like Donaldson, the founder of the New York investment bank Donaldson, Lufkin & Jenrette. That's because the chairman is just one of five commissioners who sets SEC policy. And most of the time, it's the SEC staff that initiates investigations and enforcement actions -- not the chairman. The more likely way for a chairman to influence the staff's decisions is by appointing top deputies who share his philosophy.