As expected, Rubio dropped out of the race today after being crushed by Trump in Florida, and Kaisch won his home state of Ohio, the first state where he has finished first. Trump was also victorious in Illinois and North Carolina.
Cruz didn't manage a clear win anywhere, but is trailing trump by just 0.2 percentage points in Missouri, where Clinton leads Sanders by a similar margin. Clinton won everywhere else, by a thin margin in Illinois and by a wide margin everywhere else.
717 GOP delegates have been awarded to non-Trump candidates, while 629 have gone to Trump. There are 2472 delegates in all, most of whom have already been pledged.
On the Democratic side, Clinton has won about 1/3 of the delegates including superdelegates, while Sanders has won roughly 1/6th of the delegates. So, Sanders needs about 2/3rds of the remaining delegates to win, while Clinton needs about 1/3rd of the remaining delegates to win. So, Sanders needs to win two delegates for every one that Clinton wins in the second half of the race to stay in contention. The remaining states are more favorable to Sanders demographically than the states that have already voted, but probably not that much more favorable.
It is unclear which of the three remaining candidates will receive the biggest boost from the end of Rubio's candidacy. Kaisch is the closest match as a fellow "establishment Republican", but Kaisch may not attract much support from newly liberated Rubio supporters, because his campaign seems so hopeless. Kaisch has fewer delegates than Rubio does and no hope of winning a majority or even a plurality of the delegates by the time that primary season is over. I would guess that Rubio supporters would favor Trump over Cruz on balance, but it is a hard call.
Either a Trump victory or a Cruz victory would greatly help Clinton get elected as President in a general election, although a Trump victory would be considerably easier for Clinton than a race to defeat Cruz.