Ted Cruz 

Texas Senator Ted Cruz has been attempting to run for a higher office for years and has come relatively close to beating then-candidate Trump in the 2016 election. 

Even if Trump were to run again, Ted Cruz would still have a fair shot at winning the race. Ted Cruz is an unpopular figure throughout Washington, and many Trump supporters are not ready to throw their weight behind him due to his failure to immediately endorse Trump in 2016.

One major component to a Cruz candidacy that is not being discussed is that he has previously run for President. Not many of the other names being thrown around have done this, so Cruz has a big leg up in terms of experience here.