The following graph depicts Trump’s approval ratings, according to Rasmussen Reports, since the onset of the failed effort to remove Trump from office by impeachment and trial:
Rasmussen’s polling method covers all respondents (a sample of likely voters) over a span of three days. The gaps represent weekends, when Rasmussen doesn’t publish the results of the presidential approval poll.
The Washington Post broke the story on September 20 about Trump’s July 25 phone conversation with the president of Ukraine. Thus the results for September 16 through September 20 didn’t reflect the effects of the story on the views of Rasmussen’s respondents. Trump’s approval ratings continued to rise after September 20, and peaked on September 24, the day on which the House officially initiated an impeachment inquiry. Trump’s approval ratings bottomed on October 25 but since then — despite much sound and fury, culminating in articles of impeachment and acquittal by the Senate — they have returned to where they were on September 16, given the range of error advertised by Rasmussen (±2.5 percentage points with a 95-percent level of confidence.).
If the impeachment effort had any effect, it was to strengthen allegiance to Trump among the kind of voter who put him in office in the first place — the person who sees the Democrat party as the enemy of real people. It is far too soon to say that Trump’s re-election is assured. But it isn’t too soon to say that the impeachment effort made it more likely.