Although you should try and find a slogan that ties in with your campaign points and the things that you are trying to achieve, it is also important to remember that the ones that stay in people's mind are always the catchiest ones. Catchy is key!
Slogans that rhyme are always a good bet to stick in people's minds. Something like:
"Bernice is the best, forget about the rest!"
"Don't be shy, give Bernice a try!"
These are quite traditional and obvious (maybe even a little cheesy) but should do the job for you.
Remember though- slogans don't have to rhyme, and some of the most famous advertising slogans are just short, catchy sentences:
"Just Do It" - Nike
"Finger Lickin' Good" - KFC
"I'm Lovin' It" - McDonalds
A good political tactic- as demonstrated in Barack Obama's 2008 campaign- is to choose one thing to focus on, and make that the focus of your campaign, in Obama's case it was "Change", because he wanted to focus on how his administration would be different from Bush's presidency. I think this would be a great idea if you have a specific thing you could choose?