I don't think that part is really even up for debate? While the Republicans did try to deflate the extent to which it was quid pro quo by blowing the "hearsay" defense out of proportion, it really seemed like they were focusing more on the notion that it was legitimate to pursue Ukraine investigations (and trying to 'prove' no one should listen to anything Democrats - or "Never Trumpers", or basically anyone who says something bad about Trump - have to say because it's "really" about reversing the 2016 election results

). They're selling it hard, that the Ukraine intervened in the 2016 elections, because that would justify (somehow) Trump's request. It seems like they're trying to make it sound so justified that the base doesn't even really care if there was a quid pro quo (because there was a "good" reason for it).
So the part that will eventually come to light is that the 2016 Ukraine election interference is a fabrication. According to Fiona Hill, and the New York Times, it was actually fabricated by Russia. To cover the fact that Russia interfered.
Charges of Ukrainian Meddling? A Russian Operation, U.S. Intelligence Says
In a briefing that closely aligned with Dr. Hill’s testimony, American intelligence officials informed senators and their aides in recent weeks that Russia had engaged in a yearslong campaign to essentially frame Ukraine as responsible for Moscow’s own hacking of the 2016 election, according to three American officials. The briefing came as Republicans stepped up their defenses of Mr. Trump in the Ukraine affair.
The revelations demonstrate Russia’s persistence in trying to sow discord among its adversaries — and show that the Kremlin apparently succeeded, as unfounded claims about Ukrainian interference seeped into Republican talking points. American intelligence agencies believe Moscow is likely to redouble its efforts as the 2020 presidential campaign intensifies. The classified briefing for senators also focused on Russia’s evolving influence tactics, including its growing ability to better disguise operations.