The Delaware Conundrum, Part Four

The Tea Party Express has announced the results of a poll it commissioned regarding the Republican Senate primary in Delaware. It shows that conservative challenger Christine O’Donnell is within six points of long-time at-large congressman Mike Castle. The poll has Castle at 43.7 percent and O’Donnell at 38.0 percent.
Like many others, I did not take the Tea Party Express’ polling seriously enough when it showed Joe Miller catching up with Lisa Murkowski in Alaska. So I’m not going to dismiss this poll.
I will say the following, though: (1) Delaware Republicans aren’t as conservative as Alaska Republicans, (2) O’Donnell seems like a less attractive candidate than Miller, and (3) unlike Miller, O’Donnell has little chance of winning in November, so Castle’s defeat in the primary would likely mean that the Dems hold a seat they have been expecting to lose.
UPDATE: John McCormack at the Weeky Standard has a profile of O’Donnell. He reports that (not at all to my surprise) she won’t rule out a third party candidacy if Castle is the Republican nominee. In a piece of monumentally willful blindness, she denies that there are any issues on which Castle — who typically opposes Obamacare and supports extending the Bush tax cuts — is better than a Democrat.
I hope that, in the event that Castle is the nominee, some of the more influential folks who are supporting O’Donnell will be adult enough to explain to her why she shouldn’t run as a third party candidate, and that she will be adult enough to listen.