No search engine seems to respond very well to the query "presidential candidate websites" (without the quotes), by your criterion. As an experiment, I tried it with a few of them from a private tab on my phone, looking at the first 5 pages of results.
Yandex.com (page length 10) doesn't link to any candidate websites.
DDG (page lengths 10, 20, 50, 50, 50) links to Joe Biden (page 1), Nikki Haley (page 2), RFK Jr. (page 2), Chris Christie (page 3), Marianne Williamson (page 3), Ron DeSantis (page 3), and Perry Johnson (page 4). It's missing Donald Trump, Vivek Ramaswamy, and Mike Pence.
Bing (page lengths 10, 14, 14, 14, 14) links to Joe Biden (page 1), Nikki Haley (page 2), Chris Christie (page 2), Marianne Williamson (page 3), RFK Jr. (page 3), and Ron DeSantis (page 3). It's missing Donald Trump, Vivek Ramaswamy, and Mike Pence.
Brave Search (page length 19) links to Joe Biden (page 1), Marianne Williamson (page 1), and Cornel West (page 3). It's missing RFK Jr., as well as all Republican candidates.
Yahoo (page length 10) links to Nikki Haley (page 2), Chris Christie (page 2), RFK Jr. (page 4), and Ron DeSantis (page 4). It's missing Joe Biden, Marianne Williamson, Donald Trump, Vivek Ramaswamy, and Mike Pence.
Google (page length 10) links to Joe Biden (page 1), Marianne Williamson (page 1), Ron DeSantis (page 4), and Mike Pence (page 5). It's missing RFK Jr., Donald Trump, Vivek Ramaswamy, Nikki Haley, and Chris Christie.
None of these search engines link to more than two candidate websites within the first 20 results, nor do they link to Trump's or Ramaswamy's websites, so Google is far from alone in that regard. (I haven't been able to test with Kagi Search to see if it is any different.)
Perhaps search engines are simply bound to see such a query as asking more for the concept of candidate websites in general, than for topical examples in particular.