-- And then there were four.
Hillary Clinton voted in favor of the war, which she has since said was a mistake, and Chafee wasted no time in drawing that distinction.
"My colleagues failed to do their homework," he said.
A former blacksmith from a political family, Chafee was first elected mayor of Warwick, Rhode Island, in 1992, and served until 1999 when he took over his father’s seat in the U.S. Senate after his father died. He served one term in the Senate but lost his reelection in 2006 to Democratic Sen. Sheldon Whitehouse.
He enters the 2016 race as a longshot.
"I enjoy challenges, and certainly we have many facing America," Chafee said, calling for the United States to "carefully extricate ourselves from expensive wars. Just think how better this money could be spent."
1. He Wants to Go Metric
In his announcement speech, Chafee called for the United States to adopt the metric system.
"Let’s join the rest of the world and go metric," Chafee said. "It's easy...it doesn't take long before 34 degrees is hot."
2. End Capital Punishment
"Let’s join the many countries who have banned capital punishment. Congratulations to Nebraska for your leadership," Chafee said.
3. Bring Snowden Back
4. Integrate Russia
Citing tension between Russia and Europe, Chafee suggested "strong efforts should be made to encourage Russian integration into the family of industrial nations."
5. Ban Ambassadorships for Sale
President Obama's administration has garnered media attention for posting campaign supporters and major donors in ambassadorships, a common political practice that has led to some public embarrassment for Obama.
Chafee wants to do away with that.
"As president, I would institute a ban on ambassadorships for sale," he said.
6. Warm Up to Venezuela
"I would repair relations with Venezuela, Bolivia and Ecuador," he told the crowd at George Mason.
7. Stop Drone Strikes
"They are not worth the collateral damage and toxic hatred they spread," Chafee said.
Chafee was elected governor of Rhode Island as an independent in 2010 and became a Democrat in 2013. He chose not to seek re-election in 2014. As an independent, he voted for Obama and in 2012 served as Obama’s campaign co-chair.
Unlike other democratic challengers, Chafee has not hesitated to criticize Hillary Clinton directly.
Earlier this month Chafee told ABC News about the Iraq vote, “When you hear these candidates talk about basing their decisions on faulty intelligence that is completely inaccurate. There was never any intelligence at all, never mind faulty intelligence. It was all rhetoric about weapons of mass destruction in Iraq.”
According to a recent ABC/Washington Post poll, Chafee only registered about 1 percent support among voters who are Democrats or lean Democratic compared to other candidates. He heads to New Hampshire Thursday for an event with local Democrats.
This story has been updated to reflect that Chafee won his 2006 primary but lost his general election to Sen. Sheldon Whitehouse.