The Collaborative International Dictionary of English v.0.48:

Logroll \Log"roll`\, v. i. & t.
   To engage in logrolling; to accomplish by logrolling.
   [Political cant, U. S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

logroll
    v 1: work toward the passage of some legislation by exchanging
         political favors such as trading votes