Final answer:
Parties focus narrowly due to the winner-take-all electoral system, which hinders third-party success, and their strategic positioning to appeal to moderate voters inhibits the rise of third parties.
Step-by-step explanation:
Parties in the United States often focus on alternative priorities due to the structure of elections and the strategic behavior they necessitate. One reason is the winner-take-all system, wherein only the candidate who receives the most votes wins, thereby discouraging third-party candidates who seldom receive enough votes to compete effectively. Second, parties strategically aim to appeal to a broad range of voters, tending to occupy moderate positions to capture the majority, known as 'the middle,' making it challenging for third parties to gain a distinct foothold. Additionally, the high costs and limited publicity available to third parties compared to established parties make it difficult for them to be taken seriously by voters and gain significant traction.