Signs you might be dealing with a bot or troll trying to interfere with the US presidential election
Default PFP. Not everyone who has a default PFP is a bot or troll, and a few bots/trolls actually do have custom PFPs, but enough bots/trolls have default PFPs that it's always worth looking for additional signs you're dealing with a bot/troll when you see one.
(If you're a real honest-go-goodness Tumblr blogger and you have a default PFP, then I strongly recommend you change it because many people will block you on sight.)
Default colors/layout. Again, bots and trolls don't usually put a lot of effort into customizing their blogs. Some of them fiddle around with the basic settings, but they're very unlikely to upload custom graphics and put too much effort into customizing the colors. Same as above, not everyone who has a default blog theme is a bot or troll, but enough of them do that it's worth looking for other signs of suspicious activity.
Soundbitey content. Bots/trolls don't really engage with the content of the posts they interact with. They post very generic soundbitey responses, like "You have Trump Derangement Syndrome. See a therapist," "Fuck you, I'm not voting for Genocide Joe/Kamala the Cop," "America is run by lobbies. Voting is a scam," or "Republicans and Democrats both hate us, that's why I'm voting third party." Basically, if it sounds like a regurgitated line, you may be dealing with a bot or a troll.
Lack of personal content. Bot/troll blogs may have only one post, or might just have a bunch of reblogs with nothing of substances added to them. I'm going to point out here that I've also been seeing blogs do this with pro-Biden/pro-Harris content, so I'm not sure that all of these blogs are necessarily trying to interfere with the election, or if they're trying to get attention so they can try and advertise something else down the line. Some of these blogs also post or like porn, so I suspect a lot of them are actually pornbots trying to capitalize on politics.
Here's some examples of replies from bot/troll accounts:
whodathydro is a great example of an extremely obvious bot/troll. When we go to their blog, we can see that it hasn't been customized in any way, and there's not even a single post on it.
I've also got screencaps of one-post blogs over here that you can check out. (The first one has actually gussied up their blog a little, but it clearly hasn't been used in any way an genuine blogger would use their blog - no personal content, no engagement, nothing.)
So yeah, there ya go; if you see blogs like this they are probably trolls or bots; happy reporting and blocking!