There is an interesting divide. Some of my students work, and some don't. Most of the ones who work, do well. (They got into Duke, so they have SOMETHING going for them)
And some of the ones who DON'T work much, still do well, at least in the B+ range. To be honest, Poli Sci is just not that hard. If you are smart and write well, you can write a perfectly acceptable paper in four days. Even just crunched in at the end of the semester.
An interesting article, on working and time management. The amazing thing is that you just need to work a little, every day, to succeed.
Same thing for faculty: 3 hours actual work, writing, every day and you will be pretty successful.