I've helped place enough campaign signs to know that there are a few unwritten rules; not legal requirements, not "official" in any way, and certainly not absolute, but usually followed by most campaigns -
1. Don't mess with the signs of other campaigns (every cycle, this one gets ignored by a few people, yet, in a funny way, those few exceptions illustrate how the vast majority of campaigns follow this one. There is a bit of disincentive here in the sign tampering law, but violations earn just a wrist slap; more effective are the principles of "do unto others..." and "what goes around, comes around").
2. Don't block the signs of other campaigns (this one gets tougher as the cycle grinds on, but mostly because so many signs go up that it becomes almost impossible to find a spot with clean sight lines; physics, not malice, at work).
3. Don't block non-political and permanent signs (the reason for this post).
I live in Scottsdale, a place that is so "special" that every couple of years, there is a movement to ban "unsightly" political signs as being detrimental to the image of Scottsdale.
Some call the idea "good", some call it "incumbent protection".
Most people with more than three active brain cells call it "unconstitutional" on free speech grounds.
Political signs have been restricted for safety reasons (none in medians, no blocking of sight lines at corners, etc.), but that's it.
Still, you'd think that candidates running to represent all or part of Scottsdale would at least be aware of the tender sensibilities.
You'd think that, but you'd be wrong.
At the NW corner of Pima and Chaparral roads in Scottsdale -
OK, this doesn't look too bad, right? There's a least four feet of clearance between the "Auerbach for City Council" sign and the "Welcome To Scottsdale" sign.
From a perspective of someone who can get close and analyze the signs (like a pedestrian), not bad at all.
However, signs aren't placed at busy intersections to catch the eye of pedestrians (and in most of Scottsdale, that would be a waste of time and effort anyway); they're put there to be seen by people passing by in cars.
So, the same corner, from across the intersection, viewed more as a driver than a pedestrian -
The situation regarding the "Welcome To Scottsdale" signs is even worse at other intersections. For example: NW corner of Pima and Indian Bend -
There's a reason that the anti-sign movement in Scottsdale never goes away. This ---- is one of the reasons for that.
Note to readers: Some sharp-eyed folks may notice the absence of signs of Democratic candidates in the pictures above. That's not deliberate on my part; there just aren't any at these intersections. Also, it's Scottsdale - other than the statewide candidates and the LD24 candidates (which stretches into Scottsdale south of Oak), there's only one D on the ballot, Paula Pennypacker for State Senate.
Even the most "moderate" candidates in the (allegedly) non-partisan city council race are pro-developer/chamber of commerce Republicans who are or have been members of the AZGOP's state committee.
Note2: The unwritten rules only apply to not *messing* with other candidates' signs; there's no requirement to *help* other candidates (especially opposition candidates) either -