First of all, I have a terrible record at predicting elections. In fact, the only way that I can be sure that I'm voting the way I should be is if everything and everyone I vote for loses.
Michael Moore, OTOH, has a much better record. In 2016, against virtually every other prediction, he predicted a Trump victory. In 2022, while most people predicted a "red wave", he predicted a Dem victory. Even the recent presidential debate, that most talking heads didn't know what to expect, Moore predicted Trump would lose.
I can't think of anyone anywhere with a better track record over the last 8 years.
Moore now says that Trump is "toast".

Of course Moore is right until he eventually is wrong. He also warned Harris against pivoting to the right, which she did anyway.

There is also Special Elections.

Across the country, Democrats are winning special elections and overperforming in elections they have predictably lost. And it's fueling optimism among Democrats looking at a challenging election year for both the White House and Congress.

"Polls don't vote. People vote. And that's what's been happening," says Democratic Rep. Jim McGovern, a veteran lawmaker from Massachusetts who has served in both the minority and the majority. Despite what the polls say, "people have been voting, and they've been voting Democratic. I feel really good about November – and not just about the president. I feel really good about us taking back the House."

Special election results often (but not always) predict the next election. For example, special elections in 1993 and 2009 predicted the GOP tidal waves in 1994 and 2010.

This isn't an endorsement of Harris. I simply don't trust her. OTOH, I trust Trump to be true to his authoritarian conman origins, and to not do anything to help the working class.
Even more to the point, I just can't picture 'normies' voting for a convicted felon and sexual assaulter.

The last thing I want to comment on is the future of the GOP. Few would deny that it has become a Cult of Personality. Trump is 79 years old and is in obvious cognitive decline. I'm sure that even his supporters will have to acknowledge this in the coming 4 years, which means that if Harris wins this will be Trump's last presidential run.
I honestly don't know what happens to a political party that has been captured by a Cult of Personality that no longer has that Personality around. I don't see another candidate to just swap in for Trump.