Jonathan Ernst / Reuters

In a field of Democratic presidential long shots, former Rhode Island senator and governor Lincoln Chafee, who announced his candidacy on Wednesday, may be the longest shot of all. As an authentic, uncompromising progressive, Bernie Sanders is poised to grab the bulk of those Elizabeth Warren enthusiasts who can’t reconcile themselves to Hillary Clinton. As the handsome, articulate, two-term governor of a mid-size state, Martin O’Malley at least looks like a plausible contender one day. Chafee, by contrast, in the words of Quinnipiac University’s Monica Bauer, “has the charisma of Walter Mondale wrapped in the political instincts of a small town city councilman, which he once was, and perhaps would have remained, if he hadn’t been the son of a famous political dynasty. He is George W. Bush with more intelligence but far less political talent.” And like Bush, Chafee was, until very recently, a Republican.

But Chafee could prove Hillary’s most intriguing challenger. It’s not because he’ll garner enough support to give her a scare. If anyone does that, it will likely be Sanders, who according to the New York Times is already “gain[ing] momentum in Iowa.” What makes Chafee’s candidacy intriguing is that he’s attacking Hillary on the issue on which she may be most vulnerable: her vote to authorize war with Iraq.

“I don’t think anybody should be president of the United States that made that mistake,” Chafee told The Washington Post in April. “It’s a huge mistake, and we live with broad, broad ramifications today—of instability not only in the Middle East but far beyond and the loss of American credibility.”

A version of this attack helped Barack Obama topple Hillary in 2008. That’s not likely to happen again, since Democrats care far less about Iraq this time.

But Republicans do. While foreign policy has been largely absent from the Democratic presidential campaign thus far, it’s been central to the Republican debate. And this reflects a divide in the country as a whole. A May Wall Street Journal/NBC poll found that “national security/terrorism,” which was the top concern of only eight percent of likely GOP primary voters three years ago, now ranks first, at 27 percent. Among likely Democratic primary voters, by contrast, it’s less than half that.

Iraq sits near the center of that concern. Every Republican presidential candidate except Rand Paul is telling the same story: By 2008, as a result of George W. Bush’s surge, America had won the Iraq War. But then Barack Obama snatched defeat from the jaws of victory by recklessly withdrawing US troops. Since then, the Middle East has descended into the depths of hell, and become a petri dish breeding ISIS barbarians eager to strike the United States.

The best answer to this line of attack is the one Hillary can’t give: that America should never have invaded Iraq in the first place. After all, it wouldn’t have been necessary to stitch the Iraqi state back together between 2006 and 2008, at a vast cost in money and blood, had the United States not shattered it in the first place. But Hillary can’t give that answer because she voted to authorize the war.

That’s what makes Chafee’s attack intriguing. He was the only Republican senator who voted against authorizing war. Now, as a Democratic candidate for president, he will talk about the collapse of Iraq and the rise of ISIS in a way she can’t. And the way Hillary responds to him will preview her response to the Republicans next fall.

Finding a good answer won’t be easy. On domestic issues like gay marriage, mass incarceration, immigration, and campaign finance, Hillary has shifted left in the primary, confident that she’s keeping pace not only with Democratic primary voters but with the country as a whole. But on foreign policy, the public isn’t moving left; it’s moving right. And Hillary cannot as easily adapt her views to match that shift because until two years ago, she was secretary of state.

Hillary’s greatest challenges may not be policy-based at all. They’ll likely stem from questions about her honesty, and the sense that she represents not the future but the past. But if there’s one policy question that could prove dangerous, it’s Iraq. On that subject, Lincoln Chafee is the canary in the coal mine. If Hillary can’t find an effective answer to his attacks, it may be a sign of trouble ahead.     

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