• Early 2012: Dr. Katherine Mitchell, a Veterans Affairs emergency-room physician, warns Sharon Helman, incoming director of the Phoenix VA Health Care System, that the Phoenix ER is overwhelmed and dangerous. Mitchell now alleges she was told within days by senior administrators that she had deficient communication skills and was transferred out of the ER.

• Later in 2012: The U.S. Department of Veterans Affairs orders implementation of electronic wait-time tracking and makes improved patient access a top priority. In December, the Government Accountability Office tells the Veterans Health Administration that its reporting of outpatient medical-appointment wait times is "unreliable."

• March 2013: The GAO's Debra Draper tells a House subcommittee: "Although access to timely medical appointments is critical to ensuring that veterans obtain needed medical care, long wait times and inadequate scheduling processes at VAMCs (medical centers) have been persistent problems."

July 2013: In an e-mail exchange among employees at the Carl T. Hayden VA Medical Center in Phoenix, an employee questions whether administrators are improperly touting their Wildly Important Goals program. "I think it's unfair to call any of this a success when veterans are waiting six weeks on an electronic waiting list before they're called to schedule their first PCP (primary-care provider) appointment," program analyst Damian Reese complains.

In spite of—or perhaps because of—his aversion to war, Sanders has a long history of committed service to veterans. He became chairman of the Senate Veterans Committee in 2013, and that is how he wound up at the negotiating table with Sen. John McCain of Arizona and Rep. Jeff Miller of Florida.

They were driven there by scandal. Veterans across the country were waiting months on end for appointments and the wait times were being hidden. Up to 40 veterans in Phoenix died while waiting for appointments. Hundreds never even got onto a list. And retaliation was the order of the day for those who tried to blow the whistle.

From the moment the long-gathering scandal broke into public view in April 2014, it took Congress less than four months to produce a new law—a split second by Capitol Hill standards. That it happened at all, and so fast, was a testament to the determination of Sanders and his partners to surmount the red-blue divide in American politics. It speaks volumes in particular about Sanders, who pushes for a single-payer government health system in every speech, that the law introduced a private-care option for veterans.

Of the 20 Democrats still running for president in 2020, only two -- Biden and Vermont Sen. Bernie Sanders -- were in a position to vote on authorizing President George W. Bush to go to war in Iraq back in 2002.

Sanders, then in the House, voted no. Biden, then chair of the Senate Foreign Relations Committee, voted in favor -- and like other Democrats who voted yes, has spent the years since apologizing for it as the conflict became increasingly unpopular with the American public and Democratic voters.

Biden, the Democratic front-runner, now faces opponents who do not have a voting record on Iraq and a Republican incumbent, Donald Trump, who too initially supported the Iraq war before turning against it, and then increasingly criticized Republican Party orthodoxy about American intervention abroad during his 2016 presidential campaign.

The Iraq issue dogged John Kerry in 2004 and Hillary Clinton in 2008, when it contributed to Barack Obama's meteoric rise, and again in 2016, when Sanders and Trump used it as a cudgel against her. Biden, who also ran in 2008, made the same claims that he's making today: He changed his mind about the invasion as soon as it happened.