Select the one-word substitute for the following description: A political leader who seeks support by appealing to popular desires and prejudices rather than by using rational argument.

Introduction / Context:
One-word substitution questions test how precisely a learner can match a definition to a single English word. The description given here is of a particular kind of political leader who gains support not through reasoned arguments but by playing on people's emotions, fears, and prejudices. This is a widely used concept in political science and public discourse.

Given Data / Assumptions:

• Definition: A political leader who seeks support by appealing to popular desires and prejudices rather than by using rational argument.
• Options: "rebel," "radical," "demagogue," "anarchist," and "populist."
• We must find the word that exactly matches this description.

Concept / Approach:
The precise term for such a leader is "demagogue." A demagogue is someone who manipulates public opinion by stirring up emotions and prejudices, often ignoring logic, evidence, or ethical considerations. While other words like "populist" and "radical" are related to political style or ideology, they do not necessarily involve the manipulative, prejudice-based tactics described in the question. Therefore "demagogue" is the most accurate one-word substitute.

Step-by-Step Solution:

Step 1: Focus on key phrases in the definition: "seeks support," "appealing to popular desires and prejudices," and "rather than by using rational argument." Step 2: Recall the meaning of "demagogue": a political leader who gains power by arousing the passions, emotions, and prejudices of the people instead of appealing to their reason. Step 3: Check "rebel": a person who resists or fights against authority; this says nothing about methods of persuasion. Step 4: Check "radical": someone who favours extreme or fundamental political or social change; again, this does not necessarily involve manipulative emotional appeals. Step 5: Check "anarchist": a person who believes in abolishing government and authority altogether; this is a different ideological position, not the described method of gaining support. Step 6: Check "populist": a politician who claims to represent common people against elites; this can be positive or negative and does not always imply manipulation of prejudices.

Verification / Alternative check:
In political commentary, news articles, and textbooks, the term "demagogue" is consistently used for leaders who shout slogans, spread fear, or inflame divisions in order to gain or maintain power. These leaders often oversimplify complex issues and avoid rational debate. None of the other options automatically carry this strong negative nuance of manipulating prejudices. Therefore "demagogue" aligns perfectly with the definition.

Why Other Options Are Wrong:

Option A: "rebel" describes someone who opposes authority but says nothing about emotional manipulation. Option B: "radical" refers to the degree of change desired, not the style of persuasion. Option D: "anarchist" is tied to a belief in having no government, not to the demagogic method. Option E: "populist" is broader and may or may not involve prejudiced appeals; it is not automatically negative.

Common Pitfalls:
Learners sometimes confuse "demagogue" with "democratic" because both start with "demo," but they have very different meanings. Another common trap is to choose words like "radical" or "populist" simply because they are common in political discussions, without checking whether they match the specific behaviour described. Always focus on the exact wording of the definition.

Final Answer:
The correct one-word substitute is demagogue.