But that just puts the question one step farther along: why are 59 percent of them Republicans, and only 13 percent Democrats?

From the piece "Its readers are older, higher in rank and more career-oriented than the military as a whole."

These were the folks surveyed.

It is well known that those in the OC are much more conservative than the grunts. Among those on the bottom, the distribution is much closer to the near 4?/5? mix that holds sway throughout the country.

Are Republicans more likely to enlist?

No. See above.

Or does being in the military expose you to things that make you tend to think like a Republican?

I suspect that those who go through the acadamy or otc and plan an entire military career are more often Republicans already. I doubt that the job turns them into Republicans. Why do you suppose?