By LESLIE WAYNE Wealthy Arab-Americans and foreign-born Muslims who strongly back President Bush’s decision to invade Iraq are adding their names to the ranks of Pioneers and Rangers, the elite Bush supporters who have raised $100,000 or more for his re-election. This new crop of fund-raisers comes as some opinion polls suggest support for the president among Arab-Americans is sinking and at a time when strategists from both parties say Mr. Bush is losing ground with this group. Mr. Bush has been criticized by Arab-Americans who feel they are being singled out in the fight against terrorism and who are uneasy over the administration’s Palestinian-Israeli policies. Yet the attacks of Sept. 11, 2001, and the war in Iraq have been a catalyst for some wealthy Arab-Americans to become more involved in politics. And there are still others who have a more practical reason for opening their checkbooks: access to a business-friendly White House. Already, their efforts have brought them visits with the president at his ranch in Crawford, Tex., as well as White House dinners and meetings with top administration officials. Many Arab-Americans left their countries because of political and economic oppression and are now small-business owners or entrepreneurs who say the Republican Party best represents their values.