Super Tuesday, March 15, is enormously important in this year's Presidential race. On the Republican side, John Kasich in Ohio and Marco Rubio in Florida are waging desperate fights to win their home states. If they win their home states, they will continue in the race. If not, they will each probably drop out.
Here is how things look. In Florida, Donald Trump is heavily favored; polls show him ahead, although the race has been narrowing according to some polling in recent days. One poll shows Ted Cruz almost catching up to Rubio. It seems highly unlikely that Rubio can overtake Trump, but in this crazy election year anything is possible. If Rubio wins, then he continues in the race; he gets Florida's healthy delegate count; and Trump's road to the nomination gets more complex.
In Ohio, John Kasich is the popular current governor and recent polls show a very tight race between Kasich and Trump. Trump has been hitting Kasich for his support of trade agreements that can hurt American workers, while Kasich touts Ohio's economic resurgence while he has been governor. Kasich has said if he loses Ohio he will drop out; if he wins, then he will stay in the race all the way to the convention (which is in Ohio!).
So at this point it looks like a strong likelihood, based on polls, that Trump will carry Florida; and it looks like a tossup as to whether Trump or Kasich will win in Ohio. If Trump wins both states, and Rubio and Kasich drop out, then Trump will have more delegates but it sets up a true two person race between Trump and Cruz from that point on.