I've heard more than once that it will really come down to what McConnell wants. If he sees Trump as a threat to the future of the party and decides to convict, he'll marshall enough votes. Heck, he may arrange to 'conveniently' have enough Republicans absent that the Democrats secure a conviction without many GOP members voting in favor. He accomplishes his goal without Trumpist candidates wielding the "Senator X voted against our lord and savior Trump" in campaigns.
Republicans voting to impeach Trump will kill them in the next election. It's an admission of guilt for all those who perpetuated the Big Lie.
Instead a large segment will double down on the Big Lie, because their base wants to believe the Big lie. They will fund raise on the Big Lie, start their own version of the Big Lie on every election cycle. Another segment will just completely ignore the big lie, and a tiny segment will repudiate the Big Lie and become pariahs in their own party.
There is essentially ZERO chance of conviction.
McConnell is just playing everyone, with his "leak" about supporting impeachment. He gets back at Trump by making him sweat that he might get convicted and lose his Presidential perks, he'll have Trump sweating right up until the Vote, and that might take months. He gets the democrats to waste precious time on an unwinnable trial, by letting them think there is a chance, if only they work hard enough, and long enough. Potential months of Biden's 24 month window wasted.
It's the perfect Machiavellian win-win.