Can Trump Be Stopped?

Can Trump be stopped? Not if the race doesn't get down to a two-person race really soon. My sense is that Marco Rubio has the best chance to beat Trump ("Donald Trump Should Be Worried About Marco Rubio, Not Ted Cruz"), but if Ted Cruz, John Kasich, and Ben Carson don't drop out in the very near future, it won't matter. Trump will be the GOP Nominee. God help us all.