By political tradition in the United States, when does the main presidential election campaign formally begin?

Introduction / Context:
The process of electing the President of the United States has several stages, including primaries, national party conventions and the general election campaign. Textbooks often distinguish between the nomination phase and the general election phase. This question focuses on the traditional start of the main presidential campaign, as commonly described in civics and political-science materials.

Given Data / Assumptions:

The question is about political tradition, not a legal or constitutional rule.
It asks when the main presidential campaign “begins,” implying the general election phase rather than the primary contests.
The options mention the national convention, the New Hampshire primary, the month of September and an incorrect reference to electoral votes in primaries.

Concept / Approach:
In the U.S. system, candidates compete in state primaries and caucuses to win delegates. These delegates then formally nominate the party's candidate at the national convention held in the summer. Traditionally, the general election campaign, in which the nominees of the major parties focus on winning the nationwide popular vote and the electoral college, is said to begin in early September following the conventions. Civics textbooks often phrase it exactly this way. Thus, the approach is to distinguish between the primary phase and the general election campaign, and identify the September period after conventions as the traditional start of the main presidential campaign.

Step-by-Step Solution:
Step 1: Recognise that the New Hampshire primary is one of the first events in the nomination process, not the general election campaign. Step 2: Understand that the national conventions take place in the summer and mark the formal nomination of each party's candidate. Step 3: Traditional civics teaching describes the presidential campaign as intensifying and officially beginning in September, after both major parties have held their conventions. Step 4: Option (a) says the campaign begins when a candidate is nominated at the convention. While the general election race effectively starts around that time, the standard textbook phrase emphasises “in September, following the national convention.” Step 5: Option (d) is incorrect because electoral votes are not won in primaries; primaries allocate delegates, not electoral-college votes. Step 6: Therefore, the option that best matches the traditional description is “In September, following the national convention.”

Verification / Alternative check:
Introductory American government texts often outline the electoral process in stages: first the nomination campaign (primaries and caucuses), then the national conventions, and then the general election campaign. They frequently state that the presidential campaign traditionally begins in early September, once both parties have selected their nominees. This matches option (c) very closely and distinguishes it from the primary phase or the formal moment of nomination alone.

Why Other Options Are Wrong:
When a candidate is officially nominated at the national convention: While this is a key milestone, the traditional phrasing in textbooks emphasises the start of the main campaign in September following the conventions, not at the precise moment of nomination. With the New Hampshire primary: This marks the early stage of the nomination process and is not the general election campaign that pits one party's nominee against another's. After a candidate has gained enough electoral votes in the primaries: This is factually incorrect because primaries do not allocate electoral-college votes; they allocate convention delegates.

Common Pitfalls:
Students sometimes confuse the primary season with the general election campaign and may think that the process “begins” with early primaries like New Hampshire. Others may focus on the dramatic moment of nomination at the national convention. To avoid such confusion, remember that exam questions often mirror textbook language, which states that the presidential campaign traditionally begins in September, after the conventions, when candidates turn from winning delegates to winning national voters.

Final Answer:
By political tradition, the main presidential election campaign in the United States is considered to begin in September, following the national convention.