The main danger to Barber's seat is Republican Martha McSally, a retired U.S. air force colonel who narrowly lost to Barber in the 2012 election. With one of her primary challengers -- radio talk show host Ed Martin -- dropping out, McSally is the clear GOP frontrunner in the race.

Voters have given a mixed reception to Barber's term. The incumbent has failed to build any support from his 2012 election victory and a 2013 GOP poll puts him behind McSally by a single point. While Barber has been well-liked for his centrist record, such as his support for increased border security and Second Amendment rights, his support of the Affordable Care Act is likely to become a key issue in the race.

With conservative groups spending money on advertising that links Barber to Obamacare, party demographics that have the county leaning Republican, and McSally losing the 2012 election by less than 3,000 votes, the odds are obviously stacked against Barber.

Ultimately, the race will depend on who can attract more Republican women and independents. During the 2012, McSally was able to position herself as a centrist Republican -- a likely asset in the upcoming election. Couple that with the problems in the rollout of Healthcare.gov, it seems like the election may be McSally's to take.

Photo Credit: Joie Horwitz / Tuscon Weekly