From there, Mr. Trump will head back to the campaign trail, starting with a rally in New Hampshire on Feb. 10, the night before the state’s first-in-the-nation primary race, an effort to upstage the Democrats as they try to pick a nominee to face him in the fall.

Democrats insist that Mr. Trump has been damaged by the evidence presented to the public that he sought to use the power of his office to illicitly benefit his own re-election chances. Even as they line up to acquit him, some Senate Republicans have acknowledged that the House managers prosecuting the case proved that Mr. Trump withheld $391 million in security aid to Ukraine as part of an effort to pressure it to announce political investigations into his domestic rivals.

But the public comes out of the impeachment trial pretty close to where it was when it started, divided starkly down the middle with somewhat more Americans against Mr. Trump than for him.

When the House impeached him in December, 47.4 percent supported the move and 46.5 percent opposed it, according to an analysis of multiple surveys by the polling analysis site FiveThirtyEight. Now as the trial wraps up, 49.5 percent favor impeachment versus 46.4 percent who do not.

Those numbers are strikingly close to the popular vote results from 2016, when Mr. Trump trailed Hillary Clinton 46 percent to 48 percent even as he prevailed in the Electoral College. That means that the public today is roughly where it was three years ago; few seem to have changed their minds. And the president has done nothing to expand his base and by traditional measures is a weak candidate for a second term, forcing him to try to pull the same Electoral College inside straight he did last time.

Mr. Trump is the only president in the history of Gallup polling who has never had the support of a majority of Americans for even a single day, a troubling indicator for re-election. Nine months is an eternity in American politics these days and, given his history, Mr. Trump could easily create another furor that will change the campaign dynamics, the economy could become an issue, and with all the accumulated allegations some analysts anticipate a certain scandal fatigue could weigh him down.

But Mr. Trump is gambling that he can rally his most fervent supporters by making the case that he was the victim and not the villain of impeachment while keeping disenchanted supporters on board with steady economic growth, rising military spending and conservative judicial appointments. He has made clear he will paint former Vice President Joseph R. Biden Jr. as corrupt if he faces him in the fall and will assail other possible Democratic challengers as socialists.