I do think it matters, but not in the way they talk about it. I think the potential to make serious gains appealing to Republicans to cross the aisle. They have to talk like that, but that's just not going to make any difference.
1. The anti-Trump republicans just didn't end up being a meaningful block. I'm one of them, but I can realize that we can scream all we want, and it just doesn't matter.
2. Even the "moderate" candidates are too far left for most Republicans. Most have staked themselves out to the left of Obama. It's fine, it's just what it is.
3. One element of Trump-skeptical Republicans are those that oppose his actions/behavior on religious/moral ground. Yes, he has rabid evangelical support, but it's not universal, and there are also Republican Catholics, mainline Protestants, etc. And for a large amount of those people, the Democratic flag planted on abortion up to and through birth is a big problem. I saw that Amy offered the slightest olive branch to pro-life voters, which was smart, but they'd be in a better position to peel off moderate Republican voters if they could even still talk about "safe, legal and rare".
4. Moderate and independent-thinking Republican voters have made a mass exodus off the party roles to "independent" status in the last decade or two. I'm one of them. That's one thing that gives a bit of a false impression of the Republicans moving more rightward, and being incredibly in lockstep with Trump. So when you talk about trying to pull Republican voters over to a Democratic vote, that's near impossible. Oddly, Democratic voters don't seem to have this trend...many Democrats have voted for Republican candidates since Reagan, and not changed their registration.
So, while they talk about appealing to Republicans, I don't think those numbers are enough to matter. What DOES matter though, is holding their OWN Democrats. I mean, Michigan voters identify Democrat over Republican 47-34%...there's no way that a Republican is even competitive there if Democrats aren't voting Republican.
Now, turnout matters too, but you know the anti-Trump dems are turning out this time, so I think that's slightly overrated as a reason to nominate the leftiest candidate.
I definitely think Amy/Pete is the best play available now with Biden flailing. I'm just not sure how you get there. And Frankly, I'm not sure how much it matters given the economy, and 70% saying they're better off than 4 years ago. That's almost unbeatable numbers for an incumbent, but with Trump's likelihood to step on his dick at every opportunity, you still have to prepare to win.