Well there's certainly levels to it. For example if my main issue say was downtown parking me and a bunch of fellow concerned merchants might put up posters in our shops for the candidates we believe will best protect or expand parking downtown, that's fair enough no? Ok well now people have realized we seem to have chosen 4 particular candidates to get behind in the name of parking, 2 other candidates out there are very pro-parking but they also have some politics that we think would hurt us as small business so we want to focus on the 4 we've vetted. Are we saying only these 4 care about parking? Are we saying anyone not on our list is anti-parking? Someone might see it that way, but they're probably smart enough to see that we're a group of downtown businesses so of course there's going to be a certain bias over who we're endorsing as part of the "Pro-parking slate". Things have gotten partisan at this point, but I don't think has crossed any lines.
Now, if we went a step farther and started loudly saying our 4 endorsed "pro-parking slate" candidates are the ONLY candidates who care about parking, the only candidates that want to make it easier and cheaper to drive and park downtown, that voting for anyone else but our slate is a vote for the war on cars and the death of downtown business, that's getting into the bad campaigning zone because it's claiming something that factually isn't true. We could weasel-word around it and say "we think these 4 and only these 4 are the best votes for protecting parking for workers and shoppers downtown" but the message would be clear. Also it's purely a coincidence that the 4 people we're supporting strictly about parking policies happen to be the 4 candidates that also want to lower commercial property taxes, reverse the plastic bag ban, clamp down on homeless people panhandling or sleeping near businesses, and another slate of policies our group happens to ideologically align with.