@Adam Bomb, the fact is, for registered democrats it kinda doesn't matter who the field is right now, they're not voting for the Republican nominee. Once the election rolls around most people will know who the nominee is. Fact is, every election cycle, every 3 years there's always some newspaper article saying like "Oh 50% of people can't name any candidates!" "33 % of people don't know what their own district is!" "67% of people don't know which party each candidate belongs to!" "25% of people don't know what a president is!"
The fact is, I'm no longer worried about those sorts of "the sky is falling" polling results. People are not more stupid or uninterested than they ever have been before.
At any rate, I have to say that result, if genuinely true, speaks more to a serious problem with the Republican candidates, rather than the Democratic voters.
Besides, it actually doesn't matter to them, registered Democrats can't vote in Republican primaries. When it comes to the actual election, I guarantee you, most of those people will know who the Republican nominee is.