WASHINGTON — The U.S. Chamber of Commerce, navigating dramatic cultural change that’s transforming the worlds of politics and business, plans to become less aligned with the Republican Party than it has been for decades. The largest and most powerful corporate lobbying group in Washington, D.C., is changing the way it evaluates lawmakers for the first time in 40 years, launching a $250 million capital campaign to remodel its headquarters and even rethinking its approach to regulation. Several dues-paying companies have balked as the chamber endorsed fewer and fewer Democrats over the past several election cycles.