The overall story in what we might call the Trump Impeachment Era is that support for impeachment and removal from office has grown steadily since Speaker Pelosi announced the inquiry on September 24. Trump’s approval hasn’t really fallen. But now basically everyone who doesn’t approve of Trump either strongly disapproves or wants him impeached and removed from office.
But even this isn’t quite true. Both RCP and 538 show Trump’s support falling about three percentage points over the last months. Both show a peak on September 24 (which semi-coincidentally is the very day Pelosi announced the Impeachment inquiry) steadily falling about three percentage points until today.