Would a write-in campaign by Mike Castle in Delaware hurt Christine O’Donnell or Chris Coons more — and would it make enough of a difference either way to change the election?  Rasmussen notes the problem of polling on this question, because to add Castle to the question makes it far easier to pick him in the survey than it does on Election Day, when voters will have to write out his name on a blank line.  They tailored their latest survey to take that into account, and found only 5% willing to go out of their way to select Castle:

It is possible that a write-in campaign by Congressman Mike Castle could hurt Democrat Chris Coons more than Republican Christine O’Donnell in the Delaware campaign for U.S. Senate.

A new Rasmussen Reports telephone survey of Likely Delaware voters finds Coons with 49% support, while O’Donnell earns 40% of the vote. Castle, a longtime congressman who lost to O’Donnell in the state’s GOP Primary, picks up five percent (5%). Another five percent (5%) remain undecided.

Polling for write-in campaigns is always challenging, so results should be interpreted with caution. For this survey, Rasmussen Reports asked respondents about a choice between Coons and O’Donnell without mentioning Castle. That is the choice voters will see when they enter the voting booth. However, when response options were offered to survey respondents, Castle’s name was mentioned.

Castle has not indicated that he will run a write-in campaign and it is likely that his support could increase if he were to do so. Rasmussen Reports did ask Castle supporters who they would vote for in a two-person race and virtually all said either Coons or not sure.

That should answer the question as to which candidate will suffer most from a Castle write-in campaign.  As Allahpundit has predicted, Castle will get a few of the Republicans who oppose O’Donnell and some of the moderates who don’t want to vote for a Democrat.  That latter group provided Castle with the  lead in previous polling showing him coasting to victory over Coons if Castle had won the nomination.  The people who would write Castle’s name on the ballot are those who probably wouldn’t vote for O’Donnell in any circumstance.  But, as the numbers above show, Castle’s candidacy probably won’t have a Ross Perot-like impact on the race, either.

The good news and the bad news for O’Donnell is that she’s nine back of Coons with five weeks left to go.  Even in a three-way race, though, O’Donnell has a lead among independent voters, 43/32/7.  She loses 24% of Republicans — but more than twice as many go to Coons as Castle (17% to 7% respectively).  Thirteen percent of Democrats go to O’Donnell, while only 3% would go out of their way for Castle.  O’Donnell leads among thirtysomethings 49/38 and splits the 40s with Coons, but loses the other age demographics.  O’Donnell loses most of the income demos, too, scoring a majority win among $100K+ voters and a plurality in the $60-75K demo (44/34).  Castle simply isn’t a factor in any of the demographics.

If the race comes down to Coons and O’Donnell, as it appears to have done here, there’s good news and bad news on that front.  First, the bad news: O’Donnell is seriously underwater on favorability, 39/56, while Coons is almost the reverse at 57/36.  Coons is 48/40 among independents, with 11% unsure or having no opinion, which means that O’Donnell has some narrow ability to swing that her way — except she’s at 42/47, with 10% unsure or no opinion.  The good news is that the issues, at least, favor O’Donnell.  A majority (54%) want ObamaCare repealed, with a plurality explicitly tying that to economic improvement.  Another majority of 52% say that federal government policies have the country on the wrong course.  Interestingly, despite all of the controversy over O’Donnell’s victory in the primary, a plurality consider the Tea Party good for the country (43/35).

There is a path to victory for O’Donnell, but it relies on talking exclusively about these issues and rapidly improving her favorability ratings.  Castle probably won’t do much to help or hurt her in that regard, and only will matter if this race becomes considerably closer than it is now.