They can give speech after speech but if only the bits are shown that the media want to show that fit their agenda then it has no effect if people are not willing to actually make an effort to read the entire speech or actually know where it would be found, how many of the average Americans are aware of what is published on the White House website. Sometimes I wonder how many on this board are in fact aware what published on that website.
In a way Congress has the advantage here as like the British Parliament the debates are shown in full.
Many people in Britain would be aware that transcript of parliament are published (Hansard) but would they be aware or know where to go to see the PM’s speech at a local college or factory. I am sure the same applies in the US as well.