Please, do FUCKING NOT.
His debate performance was poor against Vance. We don't need a kindly father-figure running against Republicans, we need an attack dog that knows police cold, who can articulate that tax cuts cost more in tax revenues than we make up in added jobs, economic growth, etc., someone that's going to actively piss-off billionaires and then not kiss their asses once they have power... We need a leftist populist, someone that will get people fired up.
Walz is not that guy.
One lesson that I've seen in politics over and over again is Dems running the same candidate in a rematch, and the rematch always goes worse than the original election.
Vance was polished, smooth, knew his talking points and bullshit claims cold. Walz, not so much. He didn't have good counters to a lot of the shit that Vance was throwing out. The broad consensus is that Vance handily won the debate, much like the broad consensus was that Harris trounced Trump in the debate.
He is not even close to being a white Obama. Obama is a highly skilled orator, extremely skilled debater, and a scholar. Tim Walz connects well with people--perhaps especially well with midwestern people--but he is not a particularly strong orator, is fairly weak in debates, and is definitely not a scholarly type. They may be close on policy, although I would hope that Walz would be farther to the left than Obama was.