Final answer:
Third parties' success is not hindered by acting as a safety valve or keeping the major parties accountable, but they face obstacles such as restrictive election rules, limited resources, lack of media coverage, and the Electoral College system.
Step-by-step explanation:
Obstacles to third parties' success include several factors, except for the fact that they often act as a safety valve in our political system and can keep the other two parties 'on their toes'. Obstacles include election rules designed to favor major parties, which can make it challenging for third-party candidates to get on the ballot.
Additionally, third parties often have limited resources and struggle with a lack of media coverage compared to their two-party counterparts. As a result, they are seen as less viable, and their issues may not appeal to the majority of voters, causing hesitation among potential supporters. The major parties may also co-opt issues raised by third parties, weakening their unique stance.