This is the recent Rasmussen Poll pitting Hillary Clinton against Donald Trump -- who both seem very likely to win their respective party nominations. The poll was done on February 29th and March 1st of a random national sample of 1,000 likely voters, with a 3 point margin of error.
Clinton leads Trump by 5 points (beyond the poll's margin of error). She also seems to be gaining ground in this match-up. In late December, Rasmussen showed Clinton with only a 1 point advantage (which considering the margin of error would have to be considered a tie). The poll also showed that Clinton is supported by 76% of Democrats, while Trump has the support of 65% of Republicans.
The fly in the ointment is that 24% of voters either are unsure or support someone else.