Hillary Clinton probably didn't mean to give a Washington, D.C. press event away to Bernie Sanders on Wednesday. But he gladly took it anyway.

On her latest charm offensive, the former Secretary of State returned to Capitol Hill to hold closed-door meetings with House and Senate Democrats, including Sanders—her closest rival in the polls for the Democratic nomination for U.S. president.

Emerging from that meeting while Clinton headed to another one, Sanders walked directly over to a set of microphones—typically reserved for Senate leaders—and launched into an impromptu press conference, telling reporters, "Let me welcome Secretary Clinton back to the Senate," before dryly listing off the issues the two political rivals disagree on.

Decades of bad multi-national deals, like the North America Free Trade Agreement (NAFTA), "have been disastrous for American workers," Sanders said, adding, "Secretary Clinton, I believe, has a different view on that issue," obliquely referencing her refusal to take a clear stance on current pending pacts like the Trans Pacific Partnership.

On climate change, he noted his opposition to the controversial Keystone XL pipeline, which aims to transport "some of the dirtiest fuel on this planet. I think Secretary Clinton has not been clear on her views on that issue." (In fact, environmentalists have recently raised the alarm about Clinton's potential conflicts of interest over Keystone.)

On the economy, Sanders touted his push for a $15 minimum wage and $1 trillion in infrastructure spending. "I think the secretary has not been quite so clear on those issues." (Clinton's speech on the economy this week garnered the following criticism from Robert Borosage of Campaign for America's Future: "[W]hile it checked off each reform topic, it was virtually devoid of detail.... Clinton rigorously asserted her commitment to remain uncommitted.")

The moment was another reminder of Sanders' smart campaign strategies—maintaining his underdog status, commanding media attention, and above all, remaining civil. As the Associated Press's David Espo writes:

While not exactly unplanned, Sanders' appearance at the microphones was a reminder of the type of opportunistic campaign he is running as an underdog. The cameras were there in anticipation of comments by other lawmakers, but he made use of them. As a result, he got his say — and on a day that Clinton's aides had designed to highlight her role as a front-runner conferring privately with Democrats who may well share the 2016 ballot with her.

Still, Sanders added during his spontaneous speech, "I like [Clinton]. I respect her.... It is not necessary for people to dislike each other or attack each other just because they're running for office."