Today is election day. It's not a huge one by national standards--there are a few governor's races in the South but beyond that it's a strictly local affair with few surprises in store. Normally, a year before a presidential election, there are a few races that serve as warning rockets--usually special elections from congressmen who have died.
This was most notable the case in 1991, when a Pennsylvania seat, vacated when Senator John Heinz died, went to Harris Wofford. Wofford had been the interim senator, installed by governor Bob Casey, but was far behind in the polls against former Governor and U.S. Attorney General Richard Thornburgh. At the time, then-President George Bush (Sr.) was sky-high in the polls in the aftermath of the Persian Gulf war, and it looked as if he would cruise to re-election and generally be a good year for Republicans. When Wofford instead trounced Thornburgh by an astounding 10 points--in what was a competitive state with plenty of things going the opposite direction--it signalled to a lot of folks that things weren't quite right. And, sure enough, many of the themes and issues brought up in this race ended up propelling Bill Clinton to the White House a year later. (For more information on this, I recommend Mad As Hell: Revolt at the Ballot Box by Jack Germond and Jules Whitcover.)
Of course, this is all easy to see in hindsight. At the time, no one knew that a sitting President with the highest poll numbers ever in the history of poll taking would go down in defeat. And it's easy to look at dozens of other minor races that went the other way and assume everything was fine and Pennsylvania was a blip.
Needless to say, today won't bring such things. The only major issue that could have national implications is the referendum in Ohio concerning union power, which could be seen as a rebuke against the excesses of the government in those large, rusty industrial states (specifically Ohio and Wisconsin) in curbing such power.
Still, there are plenty of local races that will have far greater implications. As per my usual dictum, if you have educated yourself on the issues, by all means go vote. If you have no idea who or what to vote for, stay home, and don't cheapen the votes of those who have researched it.