The factors that affect the outcome of a presidential race are numerous and complex. The ultimate outcome depends on many millions of individual decisions to vote for a particular candidate, and there are a range of reasons for these decisions. Some people vote on a single issue, others focus mainly on their own economic interests, and many others have a more emotional reaction to their perceptions about the candidate's personalities and values. Those who strongly support a particular party may focus much more on that party and its platform than on the individuals running for president. However, even when a candidate has the support of a major party, it is vital that they should be well-known to the public.
The most critical factors which affect the outcome are public profile and media coverage. These are linked but are not identical. President Trump, for instance, had millions of Twitter followers even before he became president, allowing him to reach a large audience directly without the need for media coverage. However, partly because he already had a very high public profile, Trump did receive an enormous amount of attention from the media in the 2016 election, far more than Secretary Clinton or any of his Republican rivals. The 2016 election presents a challenge to the conventional wisdom that funding is a very important factor in presidential races. Governor Jeb Bush was exceptionally effective at raising money, but this did not translate into votes.