Republican White House hopefuls are attacking President’s Obama’s response to Syrian dictator Bashar Assad’s bloody, five-month crackdown on pro-democracy demonstrators, saying the commander in chief wasted valuable time in mulling the situation.

Former Massachusetts Gov. Mitt Romney said the president took “far too long to speak out forcefully against Assad,” and Rep. Michele Bachmann of Minnesota said Mr. Obama should have called for the resignation weeks ago “when his regime started slaughtering and oppressing his own Syrian people.”

Texas Gov. Rick Perry, meanwhile, said the president’s call last week for Mr. Assad to step down was long overdue and that every diplomatic option should be employed to push out Mr. Assad...