Employers will often discuss a mandatory commitment when offering a job. If no commitment is mentioned at the time of a job offer, then count on a one-year commitment. Employers will occasionally ask for a two-year commitment. Not counting internships. It is harder.
Internships do help in terms of experience.
They allow one to get exposed to the workings of the Hill. If it is your goal to work on the Hill, then go there for your first job. Most entry-level jobs in congressional offices start with a low salary. Too many job seekers can't write well and suffer for their lack of skill. There are indeed, and conservative publishers do exist.