As the hoard of presidential hopefuls blanket Iowa and New Hampshire in a final primary push, at least one candidate is elated that the fall semester is coming to an end: Sen. Joseph R. Biden Jr. That’s because Senator Biden is the only candidate currently in the classroom.

The Democratic senator from Delaware has been an adjunct professor at the Widener University School of Law for 16 years, and this fall he co-taught a course on “Selected Topics in Constitutional Law,” as he has dozens of past semesters. The seminar meets Saturday mornings, and about 15 students are registered for the class.

While Senator Biden is the only presidential hopeful to currently teach on a law faculty, he’s not the only Democratic contender to have done so. Sen. Barack Obama of Illinois held a similar post lecturing on constitutional law at the University of Chicago Law School from 1993 to 2004, and Sen. Hillary Clinton of New York had a brief stint teaching at the University of Arkansas School of Law. (Former senator John Edwards says he ended his affiliation with a center on poverty at the University of North Carolina at Chapel Hill in December 2006; he also guest lectured on that campus.)

Robert L. Hayman Jr., who has taught the course with Senator Biden for the last five years, recently told a local New Hampshire newspaper that the senator is “maniacal” about not missing the class because of the campaign. The profile, which ran in The Keene Sentinel, also recounted a story of the senator flying from Las Vegas after a national debate last month to Washington, D.C. for a vote and then to Wilmington, Del. for the class.

“I just assume he doesn’t sleep at all,” Mr. Hayman told the newspaper. Perhaps the winter break can afford Senator Biden a few more minutes of shuteye.