The polls are right. Donald Trump in fact has 15%-20% more Republican support than his nearest rival for the nomination. And Trump has a "high floor" of very loyal supporters. They are not going to desert him. They comprise 30%-40% of the smaller of the two political parties.
So Trump will win the South Carolina primary tomorrow with 30%-40% of the total votes cast to 15%-25% for the runner-up, probably Ted Cruz. South Carolina apportions delegates by congressional district. Win the CD, win all the CD's delegates. Trump leads in every congressional district in South Carolina so Trump will win all of South Carolina's 50 delegates. That will increase his national delegate lead from 17-11 to 67-11. 1,237 delegates are needed for the nomination so 67 still looks a paltry sum.
March 1 is "Super Tuesday" or the "SEC Primary" as it is nicknamed this year. Alabama, Arkansas, Colorado, Georgia, Massachusetts, Minnesota, Oklahoma, Tennessee, Texas, Vermont and Virginia will vote on March 1. 595 delegates will be awarded that day and they will be awarded proportionally. Trump leads in most of those states, Texas, home American state to Senator Ted Cruz, is the only state that looks certain to go to someone other than Trump. Alberta does not vote this year. Between South Carolina and Super Tuesday are the Nevada caucuses where Trump leads by 30 points. Polls are less accurate in caucus states but Trump's lead in Nevada is so substantial that he will win the caucuses there. Trump should win 178.5-238 delegates on March 1.
So come March 2, Donald Trump should have between 245.5 and 305 total delegates. If we split that difference, 275, 22% of the total needed for nomination. That is still paltry appearing.
Experts identify two "thresholds," the 50% and the 75%. Half of all Republican delegates will have been awarded by about March 8, but proportionally. By that time Kansas, Kentucky, Louisiana, Maine, Puerto Rico, Hawaii, Idaho, Michigan, and Mississippi will also have voted. Trump's expected, approximate, 2-1 delegate lead after the 50% threshold has been reached means that his main challenger must near completely flip the race to overtake him. That is unlikely. To become reality two things need occur: first, Trump must prove to have a "low ceiling" of support in addition to a high floor and second, the field must narrow to Trump and one other candidate.
After March 14 Republican rules require that all primaries be winner-take-all. The 75% threshold with more decisive implications will be met on about April 26. All delegates from primaries March 15 (Florida, Illinois, Missouri, North Carolina, Ohio) and later, including April 26 (Arizona, Utah, Wisconsin, New York, Connecticut, Delaware, Maryland, Pennsylvania, Rhode Island) will be awarded to the candidate who wins the state.
For comparison purposes but under different allocation rules John McCain clinched the Republican nomination in 2008 when the 75% threshold was reached on March 4. In 2012 75% was reached on May 22. Mitt Romney did not clinch on 75%-day but he only had to wait a week and two more primaries to wrap it up.
If the two preconditions above are met, low Trump ceiling, one opponent, the key period to flip the race is between the 50% and 75% dates and in these primary states:
Arizona
Connecticut
Delaware
Florida
Illinois
Maryland
Missouri
New York
North Carolina
Ohio
Pennsylvania
Rhode Island
Utah
Wisconsin
