Your influence is your last successful project, or the current one if successful. If you reverse your question, you'd be asking how to demonstrate that you are qualified to lead a successful project.
The odd thing that you'll encounter when dealing with programmers is .. the wisdom of the crowd is often accurate.
You might try the following:
Publish a road map with small, attainable goals for your next release. Ensure that you leave some low hanging fruit that isn't boring. If it is a feature, let someone else completely take it over and implement it. It might be 'easy', but it needs to be a bit of work.
Finish something. If I'm going to contribute to a project, I need to see a clear end game and evidence that it can be influenced if I feel that you've gone mad. I can only base that decision on what you've done in the past.
Don't expect that you can establish the parameters of something 'awesome' and expect the world to make it happen. How often in the commit log of your repo did you actually implement something that you previously thought was difficult?
Do proper facilities exist? Mailing lists, bug tracker, wiki .. even an ugly web site for the project? I can't count on all fingers and toes how many invitations I've received (mostly due to Ohloh) to contribute to the next 'great thing' that can't even be researched when I take the time to do it.
Regarding my prior statement, I can tell when you leave easy things undone. That screams to me that you don't feel like doing it and hope someone else will. That's fine for an established project, but you don't have one of those yet. Make sure the low hanging fruit isn't boring with the same vehemence that you'd offer a job as not being 'dead end'.
Have you documented anything? This is very important. I don't want to fail my way through using whatever it is that you wrote. Give me something to start with.
Don't be a push over when it comes to patches. If you get bad patches, reject them as bad patches, gracefully. Tell people what you don't like about them as well as what you like, if anything. Don't jump just to get another brain.
I've probably left out some points, but this answer is coming to licensing. Did you use an OSI approved license? Do I need to jump through hoops just to contribute? Are you alienating people that might otherwise contribute (hint, I hope you didn't try and write a license and didn't use something viral in a library). Give me a hint of idealism and I might wish you well. Give me a hint of practicality and I'll probably send you patches. I don't get paid to make speeches. If I wanted to be like RMS (who I really respect), I would have used a condom.
If I find something cool and it looks like a level headed person is putting it together, I usually try to help out, if provided with facilities for me to do so. Otherwise, I usually just download it, say 'meh' and move on. That brings me to the last point:
You need to be responsive, friendly, level headed and articulate. I have met so many people that think they can mouth off like Linus and still garner a community. Rubbish.
Incidentally, did you use the tools that are available to draw interested people to your project?