I may be wrong on this, but I think that it comes down to this.  The democrats including Pelosi don't want to hold a vote for an "official" impeachment inquiry since doing so (should it pass) allows the President's legal team to subpoena witnesses and other evidence to the claim (which they can't do right now).  They (democrats) also don't want to expose members of certain "battleground states" to make a definitive decision one way or another.  They (the democrats) also don't have enough votes to push it through.

It seems to me that the refusal to bring this up for a vote in the HoR is more political than actual facts.  The current "impeachment inquiry" is nothing more than playing this out into election season.  There is nothing "official" regarding this current "impeachment inquiry", though you wouldn't know that if you watch the MSM and/or social media.

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