For three months, five presidential historians have been writing online columns comparing Barack Obama's initial 100 days in office with those of some of his modern predecessors. These are their final installments. The full series, along with an interactive timeline of presidential history can be found in the 100 Days blog.

By LOU CANNON

Obama, too, is misunderstood by critics as an ideologue.

By ROBERT DALLEK

Memories of L.B.J. have faded, but his stamp on society remains.

By ROGER MORRIS

Nixon was done in by character: his and that of those around him.

By JEAN EDWARD SMITH

Obama has led people to re-think their assumptions. Just like F.D.R.

By RICHARD REEVES

When it comes to mistakes, it’s hard to top J.F.K.’s early days.