Former Rhode Island Gov. Lincoln Chafee has entered the race for the Democratic presidential nomination. Chafee, speaking from the George Mason Center for Politics and International Relations in Arlington, Virginia, is seen as an extreme long shot. He expands the Democratic field to four White House hopefuls. He is also the only candidate that has been, at different points in his career, a Republican, an Independent and a Democrat. Chafee has been particularly feisty in a group that seems reluctant to go negative.

Just after announcing his exploratory committee in April, he took shots at Democratic front-runner Hillary Clinton, saying she “didn’t do her homework” when considering her vote on the 2003 Iraq War. “You may say that’s 12 years ago -- that’s a big motivator for me running,” Chafee said on CNN. “If you show a lack of judgment, a lack of doing homework then, what can we expect in the future?”

Chafee, who was also in the Senate at the time of the war authorization, was the only Republican to vote against the use of force to take out Saddam Hussein. Clinton called her vote a mistake in her memoir "Hard Choices." Chafee indicated he planned to make the issue central to his campaign, hoping to draw out the distinction between Clinton and himself.

According to a May Gallup poll, just 2 percent of Americans viewed the Iraq war as the most important non-economic problem in the country. That’s a big drop from how the issue was polling in the run-up to the 2008 election when Clinton lost the nomination to Barack Obama, who campaigned heavily on the issue, Time noted last month. At the time, Iraq was the second most important concern for voters.

Chafee, who also seems poised to focus on the environment and civil liberties, became a Democrat just two years ago at the encouragement of another Democratic candidate, former Maryland Gov. Martin O’Malley, who was then the chairman of the Democratic Governors Association. Before that, Chafee had served in state, local and federal offices, mostly as a Republican.

A graduate of Brown University, he moved his way up the political ladder in Rhode Island, joining the city council in his hometown of Warwick in 1986. He left the council in 1992 when he was elected mayor of Warwick, a position he held until his appointment as a Republican to the U.S. Senate seat left open by his father’s death in 1999. He was elected to the seat in 2000 but failed to be reelected in 2006. He won the Rhode Island governorship as an independent in 2010, and declined to run for reelection amidst poor polling numbers in the state. He voted for Obama twice and was co-chair of his 2012 reelection campaign.

Chafee could face fierce competition in both polling and fundraising. Clinton, whom 60 percent of Democratic and independent voters in a recent national poll said they would support, is also expected to spend more than $2 billion to win the White House. Chafee didn’t even register in that same poll, and was known as a reluctant fundraiser while governor.