Unless they're Joe Biden, they're starting at 48% with the popular vote.
My uncle, who spent about fifty years working at an executive level in the Ohio state Republican party had what I think is a correct view of how politics works. He said, each party candidate will attract about forty percent of the total vote. It doesn’t matter who they are, whether they’re good candidates or even if they’re dead. They get forty percent. All elections are a fight for the necessary eleven percent to make 51%. That’s where the advertising is focused and you’re generally trying to get votes from people who don’t know anything about politics.
This is why deep red Republicans are angry that the advertised policies aren’t strong enough. If they were, you can kiss that eleven percent goodby.