diff --git a/src/components/feed/PollDisplay.test.tsx b/src/components/feed/PollDisplay.test.tsx
new file mode 100644
index 00000000..1a4bee33
--- /dev/null
+++ b/src/components/feed/PollDisplay.test.tsx
@@ -0,0 +1,74 @@
+import { cleanup, render, screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { PollDisplay } from "./PollDisplay";
+
+const initialResults = {
+  options: [
+    { id: "option-1", text: "First", votes: 1, percentage: 100 },
+    { id: "option-2", text: "Second", votes: 0, percentage: 0 },
+  ],
+  total_votes: 1,
+  user_vote: "option-1",
+};
+
+const changedResults = {
+  options: [
+    { id: "option-1", text: "First", votes: 0, percentage: 0 },
+    { id: "option-2", text: "Second", votes: 1, percentage: 100 },
+  ],
+  total_votes: 1,
+  user_vote: "option-2",
+};
+
+function jsonResponse(body: unknown) {
+  return new Response(JSON.stringify(body), {
+    status: 200,
+    headers: { "Content-Type": "application/json" },
+  });
+}
+
+describe("PollDisplay", () => {
+  beforeEach(() => {
+    vi.stubGlobal("fetch", vi.fn());
+  });
+
+  afterEach(() => {
+    cleanup();
+    vi.unstubAllGlobals();
+  });
+
+  it("lets an authenticated viewer change an existing vote", async () => {
+    vi.mocked(fetch)
+      .mockResolvedValueOnce(jsonResponse(initialResults))
+      .mockResolvedValueOnce(jsonResponse({ success: true }))
+      .mockResolvedValueOnce(jsonResponse(changedResults));
+
+    render(<PollDisplay postId="post-1" isLoggedIn />);
+    await userEvent.click(await screen.findByRole("radio", { name: /Second/ }));
+
+    expect(fetch).toHaveBeenNthCalledWith(
+      2,
+      "/api/posts/post-1/poll/vote",
+      expect.objectContaining({
+        method: "POST",
+        body: JSON.stringify({ option_id: "option-2" }),
+      })
+    );
+    await waitFor(() => {
+      expect(screen.getByRole("radio", { name: /Second/ })).toHaveAttribute(
+        "aria-checked",
+        "true"
+      );
+    });
+  });
+
+  it("does not submit the already-selected option again", async () => {
+    vi.mocked(fetch).mockResolvedValueOnce(jsonResponse(initialResults));
+
+    render(<PollDisplay postId="post-1" isLoggedIn />);
+    await userEvent.click(await screen.findByRole("radio", { name: /First/ }));
+
+    expect(fetch).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/src/components/feed/PollDisplay.tsx b/src/components/feed/PollDisplay.tsx
index 6a28212b..276c3d47 100644
--- a/src/components/feed/PollDisplay.tsx
+++ b/src/components/feed/PollDisplay.tsx
@@ -37,7 +37,7 @@ export function PollDisplay({ postId, isLoggedIn }: PollDisplayProps) {
   }, [postId]);
 
   const handleVote = async (optionId: string) => {
-    if (!isLoggedIn || voting) return;
+    if (!isLoggedIn || voting || optionId === userVote) return;
     setVoting(true);
 
     try {
@@ -74,20 +74,19 @@ export function PollDisplay({ postId, isLoggedIn }: PollDisplayProps) {
   const showResults = hasVoted || !isLoggedIn;
 
   return (
-    <div className="mt-3 space-y-2" onClick={(e) => e.stopPropagation()}>
+    <div
+      className="mt-3 space-y-2"
+      onClick={(e) => e.stopPropagation()}
+      role={showResults && isLoggedIn ? "radiogroup" : undefined}
+      aria-label={showResults && isLoggedIn ? "Poll choices" : undefined}
+    >
       {options.map((option) => {
         const isSelected = userVote === option.id;
         const isWinner = showResults && option.votes === Math.max(...options.map((o) => o.votes)) && option.votes > 0;
 
         if (showResults) {
-          return (
-            <div
-              key={option.id}
-              className={cn(
-                "relative rounded-md border overflow-hidden transition-colors",
-                isSelected ? "border-primary" : "border-border"
-              )}
-            >
+          const result = (
+            <>
               {/* Background bar */}
               <div
                 className={cn(
@@ -106,6 +105,28 @@ export function PollDisplay({ postId, isLoggedIn }: PollDisplayProps) {
                   {option.percentage}%
                 </span>
               </div>
+            </>
+          );
+          const className = cn(
+            "relative rounded-md border overflow-hidden transition-colors",
+            isSelected ? "border-primary" : "border-border"
+          );
+
+          return isLoggedIn ? (
+            <button
+              key={option.id}
+              type="button"
+              className={cn(className, "block w-full text-left disabled:opacity-50")}
+              onClick={() => handleVote(option.id)}
+              disabled={voting}
+              role="radio"
+              aria-checked={isSelected}
+            >
+              {result}
+            </button>
+          ) : (
+            <div key={option.id} className={className}>
+              {result}
             </div>
           );
         }