These races ought to be scrutinized for election fraud. The Pew poll is a Leftist poll used to give fraudulent poll results so that the Democrat party can steal the election through absentee ballot fraud. The fake polling numbers before the election give the election results credibility.
You're correct but that isn't the point of these polls. Election fraud doesn't happen six months ahead. Not openly, anyway.
These numbers are to convince the public that the Democrats are viable. Other than Hickenlooper, what does the general public know about the other three Dems? It will be up to each GOP senatorial candidate to find the unpopular positions of the other and hammer these home through debates and advertising. First thing I'd do is get the Dem challenger on record supporting Nancy Pelosi and more impeachment. I expect most (maybe not Collins) will get a visit from Trump sometime next fall, too.
Also, remember that almost all the "mainstream" polls weight 5-7% more Democrats than Republicans even though more recent results have shown that there are more Republicans today than Democrats.
Liberal pollsters like PPP want to perpetuate the myth of a Democrat majority.