An interesting perspective that makes sense to me (with the disclaimer that I am not really up on my Civil War or the antebellum periods of America History). An excerpt:
For the previous sixty years, presidential Cabinets had been expanding in power and influence, to the point in the 1850s where some Cabinet secretaries (like John B. Floyd, the secretary of war under the helpless James Buchanan) actually overshadowed the presidents they were supposed to serve. Lincoln, by contrast, ruled his cabinet with an iron hand, treating Cabinet secretaries as little more than executors of decisions he had already made, rather than involving them in deliberations as semi-independent players. At the infrequent moments when Seward or Chase did challenge him, Lincoln slapped them back vigorously. In this way, Lincoln reversed the trend toward ever-more-mighty Cabinet secretaries, and established the pattern we have lived with ever since, of Cabinet subservience to presidential decision-making. By inviting real-time “rivals” into his Cabinet, Mr. Obama may find that the resemblance he conjures up may not be that of Lincoln, but James Buchanan.