Right now, Trump's base is highly motivated and energized. The Trump campaign's strategy to date has been the traditional campaign strategy that was first perfected by Karl Rove and others. Make sure your base turns out by running hard on wedge issues and then run such an awful and negative campaign that you turn off any swing voters and keep them at home. This is why Trump put Vance on the ticket. Trump's base loves Vance on abortion and immigration.
But the pivot to Harris changes things. Harris has the potential to get an Obama-esque turnout of women and minorities. The k-hive is very real and Harris will get all the #resitance voters p#ssy hat from Trump's first term back to the ballot box in droves, especially in light of Dobbs. That wasn't going to happen with Biden.
Now, the campaign is no longer for the swing voters about who is the least worst candidate. Harris has a chance to win over voters, which Biden did not have. Harris can be really effective like when she did the "that little girl was me" at the 2020 debates (even though it was heavily scripted to the point of having merch ready at the end of the debate). But she can also be very flaky when she doesn't want to answer a question and just vamps with empty politi-speak. She will have to come up with a campaign that actually reaches out to voters with real promises to improve people's material conditions instead of just saying "things are great, I will save you from Trump."
Finally, current events are a big wild card. If inflation surges, if the war in Gaza keeps roiling or some other big event happens, voters will sour on Harris. But if inflation goes in the right direction and the Fed finally lowers interest rate and there is a Gaza cease fire, then Harris will actually have some coat tails. While everyone online is pissed off, the reality is that the average voter is doing ok. People have jobs, pay is good, inflation is significant, but nothing like the 70s. Gaza matters only in Michigan where Muslim voters can swing the election. Harris has planted seeds for a pivot on Gaza to try to get the conflict under control. Jewish voters are feeling uneasy with how Netanyahu has prosecuted the war and want to see the US work with the parties to end fighting.
So, right now, I would say it looks a lot like 2016 with the popular vote going to the Dems but swing states leaning to Trump. Harris can reverse that and possibly come away with a blue wave if she puts forward an agenda that is something voters can sink their teeth into instead of a tax credit for community college that phases out based on income and has a twelve page application process.