ARLINGTON, Va. -- Former Rhode Island Gov. Lincoln Chafee officially became the fourth candidate to enter the 2016 presidential race as a Democrat, using a college campus appearance near Washington, D.C., on Wednesday to lay out an antiwar platform that also took Hillary Clinton to task.

Chafee said he wants the United States to transition to the metric system to bolster economic harmonization; would lift the government’s ban on transgender personnel in the military; is open to negotiating with Islamic State terrorists as a possible alternative to reliance on long-term U.S. military involvement in Iraq and Syria; and would permit Edward Snowden, exiled in Russia and sought by the Justice Department for prosecution, “to come home.”

Chafee, 62, said the Trans-Pacific Partnership being negotiated among a dozen countries “has the potential to set” rules for fair trade, which is an assessment at odds with Democratic presidential candidate Sen. Bernie Sanders of Vermont, who opposes the pending agreement. Chafee and Clinton come closer to President Obama’s optimism about the pact’s merits. Like his fellow Democratic contenders, including Martin O’Malley, the former Baltimore mayor and former Maryland governor, Chafee said that if elected, he would urge Congress to approve immigration legislation that includes a pathway to citizenship for an estimated 11 million undocumented migrants living in the United States.

Chafee called for an “open-minded approach” to international drug trafficking, and said he would “repair” relations with Venezuela and Ecuador if he were president. When pressed for specifics about the drug wars, he said he wanted to “listen” to the views of innovative countries and praised the United Nations, which has scheduled a special session on the topic next year.

He said he favors regulating carbon dioxide, and pointed to his co-sponsorship of climate change legislation while serving for seven years in the Senate.

Soft-spoken and geeky, Chafee gained executive experience as a Republican mayor of Warwick and was appointed and then elected as a GOP senator, following a path smoothed by his wealthy family. He lost his Senate re-election bid in 2006 to Democrat Sheldon Whitehouse.

As an independent, Chafee was elected governor in 2010. He had endorsed Barack Obama for president in 2008 and he did so again in 2012, switching his party affiliation to Democrat in 2013.

But faced with nose-diving poll numbers in 2014, Chafee decided not to seek a second term as governor.

A year later, he’s now in the presidential race, hoping that a liberal Republican-turned-independent-turned-Democrat (and the third ex-mayor in the Democratic contest) may prosper with support from younger voters, disgruntled liberals and independents, and opponents of continued U.S. military involvement in Iraq and elsewhere. Beginning in the spring, Chafee traveled to early presidential primary states, but without significant donor commitments or a budding campaign organization.

He said Wednesday he intends to seek campaign contributions, as opposed to self-funding his efforts, but said he is still “early” in that process.

Why does Chafee want to be president? “Elections are about choices and that’s the way it should be,” he said at the conclusion of a 12-minute speech delivered in front of backdrop that said “Fresh Ideas for America.”

“I’m happy to join the [candidate] choices out there,” he said.

Chafee, who answered questions posed by George Mason University students and later from the news media, came close to asserting that Clinton lacked the judgment and integrity to be the Democratic Party’s nominee. The two were colleagues in the Senate, but as members of opposing parties at the time. Chafee was the only Republican senator to reject President Bush’s push to invade Iraq in the wake of al-Qaeda attacks on September 11, 2001. He said Bush abandoned enough campaign promises during his early months in the White House that as a senator he decided to dig deeper into the administration’s assertions about weapons of mass destruction in Iraq.

He criticized Clinton’s 2002 Senate vote to authorize the invasion, as well as her impact as secretary of state.

“These are actions that people should be judged by,” he told RealClearPolitics. “The main point is the Iraq war vote. I did my homework and she did not,” he said. “She should have been suspicious of the Bush administration based on their record in those nine months before 9/11.”

Clinton has conceded that her vote -- which proved so damaging to the New York senator in the 2008 primaries against Obama -- was “a mistake.”

Without mentioning the former first lady by name, Chafee said, “It is critical that the integrity of the office of secretary of state never be questioned.” When asked about Clinton’s official State Department emails, stored on her personal server until late last year, he said the communications, plus Clinton Foundation activities now in the headlines, and lingering questions about State Department decisions were “regrettable” and undermined trust in the United States. “We just can’t have that,” he said.

Chafee said he wants to help “reinvigorate” the United Nations to tackle international issues, and redirect money spent on wars to domestic needs, such as education, infrastructure, health care, the environment, and the economy. He criticized Obama’s use of armed drones, saying it’s a policy that is “not working.”

“Let’s wage peace,” Chafee said before heading to New Hampshire.