Christine O’Donnell beat Rep. Mike Castle in Delaware’s Republican Senate primary this week, and Democrats in Washington swooned with joy. They figured that Mr. Castle, a moderate in a moderate state, would have been tough for Democratic candidate Chris Coons to beat. But Ms. O’Donnell? A pushover. She’s a sharp-edged "tea party" favorite running in a soft-edged political culture. She’ll have to answer too many questions about past statements and alleged financial improprieties. Look at the polls! She’s so far behind Mr. Coons she couldn’t find him on a GPS.

But overconfidence in politics, as in many of life’s activities, can be fatal. Coons won’t be able to coast into an office in the Senate Russell Office Building. As the old consultant adage goes, “You have to put out the yard signs if you want to make a victory speech.”

Or something like that.

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The point is, O’Donnell has pulled off one upset, and she might do it again. There are reasons for Democrats to be worried about what might happen in Delaware this fall. Here are five of them:

She's already beaten one Democrat. That’s what many of her supporters believe, anyway. They equate Representative Castle, one of the last of Capitol Hill’s dwindling band of moderate Republicans, with President Obama, in the sense that they believe Castle would vote for many administration priorities, such as an energy bill that includes cap-and-trade carbon emission provisions.

O’Donnell’s victory showed that Delaware’s GOP electorate has become more conservative. It’s no longer so dependent on wealthy, moderate voters who live in suburbs around Wilmington, a lush, rolling land studded with descendents of the DuPonts.

She's Palinesque. It is true that in the general election campaign O’Donnell will face some very tough questions, such as why she appears to have paid for living expenses with campaign funds in the past, and why it took her more than a decade to pay tuition arrears to her alma mater so she could graduate.

But O’Donnell has begun to demonstrate the ability Sarah Palin has to redirect criticism back on the “lamestream” media, in a kind of ju jitsu move that puts the candidate on the attack. She looks like Sarah Palin, a bit, and has something of Palin’s flair with set-piece speeches.

She may be no deer in the “Today” show’s headlights. At a candidate forum in Wilmington on Thursday, an audience member asked her about some controversial statements she has made in the past about abortion, homosexuality, and premarital sex.

“Yes, I have my personal beliefs,” she said, brushing the question aside.

The money is rolling in. O’Donnell had only a fraction of opponent Castle’s campaign cash until the last week of the primary campaign. Then an infusion of almost $300,000 in independent expenditures from a Tea Party Express political action committee helped push her to victory.

But checkbooks love a winner, and since then O’Donnell has collected almost $1 million in donations, according to her campaign. That’s in addition to the $42,000 check delivered by the National Republican Senatorial Committee.

GOP establishment organizations may be reluctant to contribute more to a candidate they see as having an uphill battle. But the media publicity surrounding her upset primary win is sure to bring in more dollars from individuals all over the country who support her views.

Her opponent's campaign is not trouble-free. Chris Coons has lots of name recognition in the most populous part of Delaware – New Castle County, where he is county executive. He’s got lots of money and will get help from the White House. For instance, Vice President Joe Biden (whose old seat is the one being contested) will travel to Delaware on Friday to help rally Democratic volunteers.

But O’Donnell is not the only one in the race with an interesting past. When he was 21, Coons wrote an article for his college newspaper titled “Chris Coons: The Making of a Bearded Marxist.”

“I don’t think [Delaware voters] in statements that either of us made 20 or 30 years ago,” said Coons at Thursday night’s candidate forum with O’Donnell.

Plus, Coons was not helped by a comment Senate majority leader Harry Reid (D) of Nevada made in a recent interview. “He’s my pet. He’s my favorite candidate,” said Senator Reid of Coons.

Coons’s response has been to insist that he would be an independent voice for state voters.

Chuck Norris. Chuck Norris? Action hero, roundhouse kick aficionado, subject of numerous epigrammatic Chuck Norris facts (“If at first you don’t succeed, you’re not Chuck Norris”)?

Yes. As we reported Thursday, Chuck Norris is a top financial backer of the Tea Party Express political action committee, which in turn has been one of O’Donnell’s most valuable political allies.

So get ready, Wilmington. Maybe Norris will favor O’Donnell with a campaign appearance. They could bill him as “Walker, Delaware Ranger.”

IN PICTURES: Tea Parties