Ballot access expert Richard Winger's blog is an invaluable resource to a minor party/indy enthusiast like myself.  Lately he's done some work detaling the large amount of unopposed incumbents for state legislature this year.

In Massachusetts , the Republican Party is only running 37 candidates for 160 seats.  In Illinois , over half of the seats in the legislature have only one candidate on the ballot. Of the 180 seats in the Georgia legislature, 141 have one candidate on the ballot.  These are all quite disheartening, but Arkansas takes the cake.

There is no major party opposition for US Senate or House in Arkansas.  Sen. Mark Pryor's (D-AR) only challengers are an independent and a Green.  In the House, District 1 is an unopposed Democratic seat.  Districts 2 and 4 feature a Democrat vs a Green, and District 3 features a Republican vs a Green.  The Arkansas state senate is even worse: 17 of 18 seats have one candidate on the ballot.

A particular oddity is in the 39th state house district where there is only one candidate on the ballot, who is a member of the Green Party.  A Democrat who filed was removed from the ballot by the Democratic Party.  He is appealing to the Arkansas Supreme Court to have his name reinstated.

I think we can point to two reasons why so many candidates are unopposed, the first of which is gerrymandering.  In most states, the state legislature draws the districts usually in order to favor one party at the expense of the other.  In this manner, even if there was opposition, it would be only token opposition.  When seats are so strongly partisan, no one bothers to challenge an entrenched incumbent because opposing such a candidate is only an exercise in principle; such a candidate knows that they can't win absent a major scandal.  Gerrymandering effectively makes a particular party's primary the general election with the real general election a simple formality; this is often the case in heavily Democratic urban areas. 

The second reason is that the two-party mindset is ingrained upon or political psyche.  Independents and minor party candidates are usually seen as kooks or radicals and not given a fair shake.  In most states, it is relatively easy to join a major political party and run in that party's primary.  We are used to seeing two names on the ballot for each office.  A third or fourth name signifies someone who "couldn't make it" in a mainstream party -- someone who certainly isn't going to win, and therefore is not worth a vote.  On the flip side, independents and minor party candidates often jump at the chance to run against an unopposed major party incumbent, but are discouraged due to unequal and discriminatory access to the ballot.

In any districting system there will always be pockets of strong support for a particular party.  However, we are alone in having so many candidates running unopposed for office.  Canada and the UK have the same voting system, but there is almost always major party opposition for every seat.  In my studies there has never been anyone in recent history who ran unopposed in either country.  What makes us different and what can we do to fix it?  Or have I assumed too much?  Is this lack of political choice even a problem?  Does it really matter if there is at least token opposition in each district?