*Whossorry
*
I think Pelosi feels that starting impeachment so close to campaign season will provide a 'rallying point' for Scrotus' supporters. A single issue to unite them behind him and give them a reason to continue to support him. It will also allow him to play the 'Persecution Card'. Plus when the Senate fails to impeach, he will claim vindication, just as he did with Barr's spin on the Mueller report.
To continue investigating him will allow a flow of revelations and information about him and his nefarious doings without the 'stigma' of impeachment proceedings. Which he would do his best to turn into a 3 ring circus of misinformation and obstruction.
The focus now should be on defeating him in 2020. If he's re-elected (God forbid) then turn the big guns on him and impeach away.