[VictorPath]

One counter-vailing fact is Republican internal polls showed Trump losing up until election night in 2016. Polls they did for themselves, which they did not share at the time, showed him losing.

Aside from this, to influence opinions with sharing polling information, one just needs to change the question, or the audience, or both. "Should the US seek peaceful resolutions with Russia" will get a different answer than "Should Biden oppose Russia's military buildup on Ukraine's border". You can tailor the question to the answer, and have Americans either supporting or opposing abortion, or whatever.

Also, a poll of everyone will yield different results from a poll of, say, likely voters. You have to look to who is polled along with what is polled.

With these things done, there is little need to fudge the numbers, other polling organizations can ask the same question to the same demographic and get similar answers.