I rarely flake out on plans or commitments, but once in a while if I really just don't feel like going out I might make up some believable excuse not to go - but it's quite rare.
An AS friend of mine hates it when people flake out & doesn't want to flake out himself - but he knows himself well enough to know that he might change his mind about going somewhere or doing something, so his automatic intuitive solution is to almost never commit to anything. He'll express an interest and say flat out that it sounds cool but he doesn't want to commit because he doesn't know how his schedule might change, if something else will come up, or if he might not feel up to doing anything. So he'll give a tentative yes & then I'll simply check back in with him closer to the date/time and see if he's up for it - sometimes he is, sometimes he's not for various reasons - but he's always appreciative of the invites. Since he never commits, he never flakes out, so is never rude about it. Also, he doesn't have to explain much to me about why he doesn't want to go out - I already know he likes to stick to his routine & comfortable places and faces etc and accept that fully.
But yeah, maybe try something along the lines of what he does? Don't say yes and commit.. express interest and indicate that you'll see how your day goes and if you might be able to make it to some invite.
Also, in the case you wrote about.. it doesn't sound like you flaked out too badly.. especially since all of the details & logistics of the event evolved from what you knew about it at first. It's not your fault you didn't have all the info to make a proper decision and politely decline the invite right off the bat.
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No
for supporting trump. Because doing so is deplorable.