It's looking very likely that the Republicans will nominate Donald Trump, and the Democrats will nominate Hillary Clinton. What happens if those are the nominees? Some in both parties are unhappy with that, and are saying they will not vote for the party's nominee.
The Rasmussen Poll did another survey to see which party might be hurt the most if these candidates are the nominees. The survey was done on April 25th and 26th of a random national sample of 1,000 likely voters, and has a margin of error of 3 points.
Their poll showed that about 25% of Democrats say right now that they would not vote for Clinton, while 31% of Republicans say they would not vote for Trump (and another 3% are unsure).
I believe that most of those people will eventually, if grudgingly, fall in line and vote for their party's nominee -- but it is clear that the Republicans have a bigger job to do in winning back voters than the Democrats have.