Decline grad school for fellowship? So, I have a bit of a dilemma on my hands. 

I took a gap year after graduating from college, and I thought I was going to go straight to grad school after. I got accepted to multiple programs, and I already declined all of the programs except one. 

Here’s the problem: I also applied to a competitive, two-year fellowship with a government organization, and I made it to the interview stage! And now, I changed my mind about going to grad school and I’d like to get more experience on my hands. Unfortunately, we won’t know if we get the position by July. Point is: there might be a chance I might decline the school after I accept my intent to go there if I get the fellowship. I know that grad schools (I applied to both public health and heath administration)  allow deferment for only a year, but I’d like to have a backup plan just in case I don’t get the fellowship (which is go to grad school). 

So let’s say if I do get the fellowship, should I just be honest with the school I accepted and tell them I want to do the fellowship? Or take a risk and decline the school and I hope I get the fellowship?

If I do the former, I just hope that this won’t hinder me from other schools considering  my application the next time I apply to grad school. I’m applying right after the fellowship, and this time I INTEND to go back to school. 

Thanks.
A major fellowship may be enough to get a grad school to agree to a longer deferment. However, even if they're not willing to extend you a two-year fellowship, when you reapply, you will have that major program under your belt, and will be a stronger candidate than many in your field applying straight out of undergrad. 

So I wouldn't worry too much about this in terms of your long-term grad school prospects.