NBC senior political editor Mark Murray tweeted out these three charts on Monday morning:

Those three charts tell the story of the next steps in the presidential race. But before we get to them, let's look at the state of the delegate fight now that 20 states or territories have voted.

Billionaire Donald Trump has 392 delegates to the 305 that Sen. Ted Cruz (Tex.) has; Sen. Marco Rubio (Fla.) has 153, and Ohio Gov. John Kasich has 35. A candidate needs 1,237 to formally clinch the Republican nomination.

Now, back to the charts from Murray.

If Trump sweeps Ohio (66 delegates) and Florida (99 delegates) on March 15, his lead over Cruz would go from less than 100 to nearly 300. (Florida and Ohio are winner-take-all states, meaning that if you win the statewide vote, you win all of that state's delegates.) Trump would then need to win only 52 percent of the remaining delegates to be the nominee. That's a slightly better pace than the 45 percent of available delegates Trump has won, but he would almost certainly make it to 1,237, with coastal states' votes coming, including delegate-rich ones such as California (June 7) and New York (April 9).

If Trump wins Florida but loses Ohio to Kasich — the most likely scenario other than a Trump sweep — Trump's lead over Cruz would be just over 200 delegates.  That makes his path to 1,237 more complicated as he would need to win 59 percent of the remaining delegates to formally secure the GOP nomination before the July convention in Cleveland. That's a tougher bar for Trump to reach but would remain doable, given that the states set to vote after March 15 will be, in the main, more favorable to Trump than Cruz.

Should Rubio win Florida and Kasich win Ohio, it's a near-certainty that no candidate will come close to getting the required number of delegates to win the nomination. Trump remains the only one with an even-marginally viable path, but he would need to win 69 percent of the remaining delegates after March 15 if he loses Ohio and Florida. Mathematically possible but practically very difficult.

There'll be lots written between now and March 15 — including in this space — about the GOP race. But here are the four things you need to know:

1. Donald Trump is, realistically, the only Republican candidate who can get to 1,237 delegates before the convention in Cleveland.

2. If Trump wins Ohio and Florida, he will be the Republican nominee.

3. If he loses Ohio and Florida, this race is going to be decided at an open convention.

4. If he wins Ohio or Florida but not both, he could — but probably won't — get to 1,237 before the convention.

That's it. That's the whole story. What happens in eight days' time will set the course for the remainder of the race. And it's hard to see that course changing all that much between March 16 and July 18, the opening day of the convention.