Mitt Romney. (Jacquelyn Martin/AP)

In his most extensive remarks yet on the 2016 presidential race, Mitt Romney on Tuesday said he shared the feeling of many Americans that Washington has failed them and urged national leaders to take on big problems, including issues that the GOP has rarely put at the fore during the past year, such as climate change, poverty, education and income inequality.

“We’re just mad as hell and won’t take it anymore,” Romney said of the national electorate in an appearance at Babson College in Wellesley, Mass., where he harshly criticized “the failure of current political leaders to actually tackle major challenges, or to try at least, or to go out with proposals.”

“Think for a moment about the major challenges you believe this country faces and tick them off in your mind and ask, ‘Are we making any real progress on any of them?’ Romney said, striking an exasperated tone as he turned to the crowd.

Romney then listed a range of topics that are priorities for Republicans and Democrats, from the national debt and the “scale of entitlements” for the former to “global warming” and poverty for the latter, and argued that little to nothing has been accomplished on those fronts in the past few years.

Romney said it is time for members of both parties to say, “Here’s what we’re going to do finally to fix education, here’s what we’re going to do to end generational poverty,” adding that addressing the “income gap” should also be high on the agenda.

Romney’s message — partly channeling the surge of populism nationally but focusing on issues that have not animated the race for the Republican presidential nomination — signaled that the 2012 GOP nominee’s pitch has evolved since his bid, with more emphasis on policies that might benefit people who are struggling to get by.

Romney’s comments come as Sen. Marco Rubio of Florida and others in the Republican race are finding it difficult to counter the rise of Donald Trump, and as Romney remains undecided about whether he will endorse a candidate.

Donald Trump cruised to victory in Nevada, building a broad coalition that left his two rivals trailing far behind heading into Super Tuesday. The Washington Post's David Weigel talks about what this means for Trump 's chances of securing the GOP nomination. (Alice Li/The Washington Post)

Romney’s sit-down conversation at Babson was moderated by Kerry Healey, the college’s president, who served as Romney’s lieutenant governor during his gubernatorial tenure in Massachusetts.

While being careful to avoid embracing the politics of Trump or Vermont Sen. Bernie Sanders, Romney repeatedly pointed to both contenders as indicators of how elected political leaders in both parties have stumbled.

“Certainly part of what is behind the energy and the passion for Donald Trump on the Republican side and Bernie Sanders on the Democratic side is the frustration and anger people feel in this country,” Romney said.

Romney described their success as a “projection on them by the American public that they’re at least going to do something. They’re going to make something happen.”

But Romney warned that if Sanders and Trump win their respective nominations, a third-party bid by former New York mayor Michael Bloomberg may emerge. “He’d probably be getting in,” Romney said. “I think he would recognize that there is a chance for a centrist candidate.”

When asked by an attendee whether he would endorse a Republican in the coming days, Romney was cagey.

“The answer is, I’m not going to tell you,” Romney said, drawing laughs. “I am very involved and will be increasingly involved. I’m involved now behind the scenes with a number of people who are running for president. And I did not anticipate endorsing but I probably will at some point. I don’t know who yet.

“One thing I’ll mention is that before I would endorse somebody, I’d want to see their past taxes. We’ve got Cruz, Rubio and Trump -- haven’t released their tax returns. And I’d like to know, you know, have they paid taxes? How much money they made. So we haven’t seen that yet. I’d like to see that. But as we go along here, as the field narrows, I may endorse but that’s not anything immediate.”

After speaking at Babson, Romney attended a dinner at Healey’s home, where he was joined by a group of close friends and former officials from his 2012 campaign such as Bob White, Spencer Zwick, Beth Myers and Peter Flaherty.

People familiar with the gathering said the private event was social.

This story has been updated.