The sufficient condition: seventeen (17) Republican states have enacted laws restricting access to the voting booth, restrictions so onerous as to defy both common sense and the spirit of democratic governance. These laws guarantee that the people who would vote against Mr. Trump will be blocked from participating in the election. They simply will not be able to vote. For example, to vote in the State of Texas, a gun permit suffices. A college ID does not. So it is in 17 of 50 US States.
The movement to block access to voting has been a long term effort, a reaction to the election of the first African American president, and it is now too late to do anything about this.
Rather than effectively fighting voter disenfranchisement, Democrats were convinced that this was a Black issue (Florida 2000, Ohio 2004), and therefore unworthy of serious consideration. They were also distracted by fabricated controversies, like the birther issue (promoted by one Donald J. Trump). Finally, having the nation's largest news channel bring forth an unprecedented level of misinformation and vitriol aimed at the current President and the presumptive Democratic nominee served to create an atmosphere of mistrust. The financial crisis added to the level of dissatisfaction.
What this means is that Mr. Trump can insult Mexicans all he likes. He can insult immigrants and members of other minority groups as well: they are not going to be able to vote.
Thus, Mr. Trump's behaviour is not accidental. This brings us to the necessary condition.
Having blocked access to the polls, all that is required to push Mr. Trump into the White House is a surge in voting by disaffected, uneducated, low to moderate income white voters. This, the biggest demographic in the election, must be incentivized to participate. Mr. Trump's behaviour and language does so.
Given the above, popular voting victory is assured. The Electoral College, the only votes that really matter, will be forced to follow.
Game. Set. Match.
Welcome, President Trump.