Think tanks and other organizations will often post all of their material on the web.
But many articles published in scholarly journals and popular (general interest) magazines are not freely available on the web although it sometimes appears that way.*
More importantly, search engines are serving up content for reasons other than the research needs of scholars. Their reasons, frankly, are to drive business to their advertising content, or to collect data on your interests (to sell to advertisers). Sometimes, especially when a web search seems to work well, it's difficult to keep that in mind.
Looking for scholarly journal articles?
Search a library database, especially a database tailor-made for your discipline (in this case, Political Science).
*The library purchases subscriptions to these journals so that students and faculty will have access to the articles even when they are simply searching the web. The Google search engines sees the Cornell IP address and provides access through the Cornell Library subscription). Off-campus, you don't have the same access.
*When you are searching the web off-campus, Google won't see the Cornell IP and you won't have the same access (see Passkey).