Lincoln Chafee was the only Republican senator to vote against the Iraq War. Now neither a senator nor a Republican, the war is a major reason he is contemplating a run for the Democratic presidential nomination.

Although Iraq went unmentioned in a halting announcement video of sorts, Chafee has said Hillary Clinton’s vote for the war is disqualifying and that the 2003 invasion helped trigger much of the chaos rippling through the rest of the world.

“I don’t think anybody should be president of the United States that made that mistake,” he told the Washington Post. “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. There were no weapons of mass destruction.”

Chafee would be an unusual challenger. In just the last ten years, he has been a Republican, independent, and a Democrat. In fact, his announcement he was exploring the Democratic nomination came less than two years after he joined the party.

Nor would this be the first time the adjective “unusual” has been used to describe Chafee. Born to wealth and privilege, he was known for drug use and a lack of direction in his early years. He hailed from one of Rhode Island’s founding “five families.” His father, John Chafee, was perhaps the last great Rockfeller Republican.

After graduating from Brown University in 1975, he attended horseshoeing school in Montana and spent some seven years working at harness racetracks. He more or less blundered into politics, moving from a seat on the Warwick, R.I. city council–where was nicknamed “Missing Linc” and criticized for a lack of engagement with local issues–to the mayoralty, then the U.S. Senate upon his father’s death.

Rhode Island Republicans didn’t have a deep bench and the younger Chafee had expressed interest in running for the seat in 2000, when his father planned to retire. So the state’s GOP governor appointed him to fill out the remainder of the term.

Yet Chafee to a large extent followed in his father’s footsteps. He was elected to the Senate for a full term in his own right in 2000, where he became a high-profile liberal Republican. Control of the Senate briefly hung in the balance as Chafee considered switching parties, but another GOP liberal, Jim Jeffords of Vermont, jumped first.

Chafee beat a conservative primary challenger in 2006, but lost reelection in part because of the Iraq War he had voted against. He left the Republican Party and was elected governor of Rhode Island without the support of either party. He ended up with poor approval ratings and declined to run for reelection.

By most measures, Jim Webb would be the more credible antiwar challenger to Clinton, even with his well publicized misgivings about the Iran deal. A fellow one-term senator, Webb has a formidable military background while the moppy-haired Chafee looks like he should either be attending classes at Brown or shoeing horses somewhere.

In a 2001 New Republic profile, Michael Crowley compared Chafee to the Chauncy Gardner character in the Peter Sellers film Being There. It’s a backhanded compliment, as Gardner’s “simple aphorisms about gardening are misinterpreted as profound political insights.”

Chafee, however, has shown a willingness to actually criticize Clinton on foreign policy and her coziness to Wall Street in a way that Webb has hesitated to do and Martin O’Malley probably can’t if he is interested in a longer term career in the Democratic Party. And while Chafee was a Republican, he was never as conservative as Webb. In 2005, Clinton and Chafee had identical American Conservative Union ratings.

“She needs to be asked hard questions about her Iraq war vote and her tenure as Secretary of State and where she wants to take this country,” Chafee told The Hill. “I think she’s tone deaf on some of these issues.”

On Iraq, in particular, he says, “I did my homework and I looked at the evidence….she got it wrong.” He is also not shy about tying the war to the rise of the Islamic State in Iraq and Syria.

The main reason Hillary Clinton did not win the Democratic nomination, and probably the presidency, in 2008 was that she voted for the Iraq War. It would be fitting if her main Democratic challenger were one of the seven Republicans who voted no.

W. James Antle III is managing editor of the Daily Caller and author of Devouring Freedom: Can Big Government Ever Be Stopped?