The D's ABSOLUTELY NEED an impeachment between Thanksgiving and Christmas. Otherwise, they have no hope at all of winning the election. What they don't see is that if they impeach based on the current lies, they won't win. And, if they don't impeach, they won't win. And finally, even if they do impeach Trump, they still won't win in November.
Those are very nice theories.
However, the Democrats had to forget about election theories, quit worrying about the damned election, and deal with the repeated behavior of a President who kept seeking foreign assistance for his own election interests.
It's your prerogative to condone the President's behavior, and the Senate probably will condone it, but impeachment is not primarily a political calculation by the Democratic leadership.