WASHINGTON — In one way at least, President-elect Donald J. Trump has already surpassed all of his recent predecessors. It took Barack Obama 18 months in the White House for his approval rating to slip to 44 percent in Gallup polling, and it took George W. Bush 4½ years to fall that far. Mr. Trump got there before even being sworn in.

Indeed, Mr. Trump will take office on Friday with less popular support than any new president in modern times, according to an array of surveys, a sign that he has failed to rally Americans behind him, beyond the base that helped him win in November. Rather than a unifying moment, his transition to power has seen a continuation of the polarization of the election last year.

Where other presidents used the weeks before their inauguration to put the animosities of the campaign behind them and to try to knit the country together again, Mr. Trump has approached the interregnum as if he were a television wrestling star. He has taken on a civil rights icon, a Hollywood actress, intelligence agencies, defense contractors, European leaders and President Obama. The healing theme common at this stage in the four-year presidential cycle is absent.

“He seems to want to engage with every windmill that he can find, rather than focus on the large aspect of assuming the most important position on earth,” Senator John McCain, Republican of Arizona, said on CNN on Tuesday. “And obviously, apparently, according to the polls, many Americans are not happy with that approach when he has not even assumed the presidency.”