Push lawn mower won t start?

I have Lawn- Boy push mower, like the one linked below:

http://www.homedepot.com/p/Lawn-Boy-21-in-High-Whe...

It was left in the rain twice, but has been used since then with no issues. I went to try to cut the grass today because it has been a while and it was fairly long and a little bit damp. Anyways, it would start and work for a few feet then turn off, and I d have to drag it back to the sidewalk to restart it because it wouldn t start in the grass. And this continued until after about 5 cycles, when it stopped turning on.

I cleaned out underneath it to the best of my ability to get rid of the clumps of wet grass but it won t start. It has gas and everything, but won t turn on.

Any ideas that I can try before either calling in someone else or getting a new one? Thanks