The thing being suggested here is that the campaign of the incumbent is reading all the communications of the campaign of the challenger. I don't think anything of the sort actually happens or is really that easy to (completely secretly!) make happen, but that's the proposed scenario.
'Congressional investigators determined that "targeting of US political figures would not occur by accident, but was designed into the system from the start."'
So yeah that might still be going on. Signal etc. make it harder but it's not like the NSA isn't hacking endpoints so hard to say if it's actually secure. We can only hope the next Snowden will let us know if NSA's spying on the opposing political party.
I don't mean that, I'm just pretty sure the person you are replying to meant that. As to the other stuff, no, even if your security services are collecting this sort of thing, by design or not, it doesn't mean it's in your daily briefing, let alone available to your campaign. If it was, Nixon wouldn't have needed to hire a bunch of incompetent cosplayers to be 'Plumbers'.
My kids tested sending https://kamalaharris.info and https://joebiden.info to each other on Instagram, in private messages. The sender would see that the message was successfully sent, but it would never arrive.
Another case is that the person who ran the primary campaign for Kamala Harris now works at Twitter, where he blocked an opponent's campaign account.
