I don't see how any of the other candidates can topple Trump at this stage. Sanders might be able to catch up to Clinton but even then Clinton's experience in running this race 8 years ago is probably going to take her across the finish line. I can't make head or tails of why Trump is leading the race amongst the Republicans though.
Polling to this point suggests that the leaders will continue to be leaders even after Super Tuesday. With Trump and Clinton sitting firmly in the drivers seats of their parties, there is little reason to believe things will change. If something does change, it's more likely to be Sanders overtaking Clinton than Trump succumbing to another candidate.
Donald Trump and Hillary Clinton going to emerge victorious on Super Tuesday because the voting base, and polls indicate as much, are in tune with both of their political stances. Clinton appeals to the more moderate liberal left, while Trump appeals to the anti-establishment sentiment that is permeating the GOP.
It's unfortunate, but I do believe that Trump will be the big winner in the Republican race, and I am quite confident that Clinton will be triumphant in the Democratic race. They both have very large leads over their competitors. Clinton stands to lose a couple of states and come close in a couple of others, but I think in the end she will pick up many more delegates than Sanders. The Republican race is a little more volatile right now. Although most recent polls have shown Trump leading in all states but Texas today, I think that could change when the votes actually come in. There has been a lot of negative press for him in the past week or so, and I wouldn't be surprised if his momentum faded.