As a registered Independent voter and a libertarian philosophy having person, I am very interested in hearing from all credible candidates running for elected office. That is, in fact, my first criteria to my taking a candidate seriously, to be credible.
What then, to me, is a credible candidate? First it's someone who has done the legwork to be able to be identified and recognized as a candidate. Someone who as gotten their name as a candidate for whatever office on the ballots of all the involved voting locations.
Want me to take you as a credible candidate for state senator? Then make sure you have done the footwork to be identified and listed in the counties within your chosen constituency. President of the U.S.? Then if there are 50 states (and there are) then you should have done the necessary footwork to be on all 50 states ballots.
For me, this shows that you take the job seriously enough to make sure everyone is informed and able to identify you as a candidate. To show up and not have done the work to accomplish that most basic step indicates to me that you don't take this serious enough yourself. You're playing at it. If you don't take it seriously, I sure won't take you seriously.
The next thing for me to take someone as a credible candidate is to make the effort to inform people about your candidacy and be accessible to potential voters, ALL potential voters. If you're just talking to the people you prefer or the ones who can give you statistical advantages then I see you as just trying to game the system. It's more about you than it is about the job you're trying to do.
Be consistent in your message. The biggest red flag of someone who isn't credible is that they say whatever they have to to pander to who they are talking to at the time even if it contradicts what they said to someone somewhere else. Again, this points to it just being about you and trying to game the system. If you really have a position on something, stick with it. People may not agree with you on it but they will likely respect you for standing firm on a principled position. People like to see that their elected representatives have a backbone and won't abandon their principles at the first chance.
If you won't or can't do the footwork, f you aren't making yourself accessible to as many people as possible and if you aren't putting out a consistent message then I don't see you as a credible candidate and I won't bother to pay attention to you.