The Republican-Democrat contest is the hottest in years. The voter debate is about which candidates will be the most likely to lift the United States out of a morass marked by near-double-digit unemployment, sluggish economic growth and a terrifying $1.29 trillion budget deficit.
As campaigning time wanes, it's clear that an increasing number of seats are vulnerable.
"Let me tell you something," U.S. Vice President Joe Biden wrote Monday. "I've been around campaigns for a long time and I have never seen a midterm election with this many races in play."
Experts described this campaign season as more volatile than most because of a major possible shift in power.