WASHINGTON — Hillary Rodham Clinton has a third underdog challenger for the Democratic presidential nomination.

Former Rhode Island Gov. Lincoln Chafee entered the race Wednesday, casting himself as an anti-war candidate who opposed the invasion of Iraq back when Clinton supported it.

“We must deliberately and carefully extricate ourselves from expensive wars,” Chafee told a half-full law school classroom at George Mason University in Virginia. “We need to be very smart in these voluble times overseas.”

With his announcement, Chafee became the biggest longshot among Clinton rivals who have a long way to go to avoid becoming historical footnotes in 2016.

Chafee, a former Republican turned independent who joined the Democratic Party two years ago, has made little effort to set up a competitive campaign operation, beyond a few visits and calls to activists in the early voting states of New Hampshire, Iowa and South Carolina.

The policy prescriptions in his speech included some probable non-starters, such as moving the U.S. to the metric system.