To many Republicans, Speaker Paul D. Ryan’s proclamation on Thursday that he was not prepared to support Donald J. Trump seemed to be an opening bid. In truth, it was more like the final word.

Although party leaders furiously brokered a meeting between the two men at the Capitol next Thursday, it is likely that only substantial changes in Mr. Trump’s language and tenor, not just minor calibrations on policy positions, will be needed to bring Mr. Ryan to his camp.