ROMNEY: Donald Trump and Bernie Sanders are part of the same 'mad as hell' phenomenon
"We're just mad as hell and won't take it anymore," he said of the electorate on Tuesday, per The Washington Post.
"The failure of current political leaders to actually tackle major challenges, or to try at least, or to go out with proposals," he added, speaking at Babson College in Wellesley, Massachusetts.
Romney said he shared feelings with many Americans who feel betrayed by their government. The former presidential candidate discussed poverty, climate change, income inequality, and education as some of the biggest problems facing the nation, according to The Post.
"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?'" The Post quoted Romney as saying.
He later added: "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."
Trump, the GOP frontrunner, won his third consecutive state on Tuesday with his victory in the Nevada caucuses. Sanders, a Vermont senator, has beaten Democratic frontrunner and former Secretary of State Hillary Clinton in New Hampshire and finished closely behind her in Iowa and Nevada.
The Post said Romney attributed the candidates' success to a "projection on them by the American public that they're at least going to do something - they're going to make something happen."
Romney argued that lack of progress on reining in the national debt and entitlement programs had Republican voters fuming, The Post reported. He also said a lack of progress on climate change and poverty had Democrats up in arms.
The former Massachusetts governor has yet to endorse a candidate in the 2016 race. It was reported that after former Gov. Jeb Bush of Florida dropped out on Saturday, Romney would endorse Marco Rubio, a Florida senator. But Rubio's campaign called the reports unfounded.
According to The Post, Romney also said at his Tuesday event that if both Sanders and Trump won party nominations, he expected to see former Mayor Michael Bloomberg of New York enter the race as a centrist alternative.
"He'd probably be getting in," Romney said of the scenario. "I think he would recognize that there is a chance for a centrist candidate."
In September, Romney said he didn't think Trump would be his party's nominee.
"I will support the Republican nominee," he said then. "I don't think that's going to be Donald Trump."
Trump has repeatedly criticized Romney for losing the 2012 election to President Barack Obama. Trump has even suggested that he would have won the White House that year had he been the nominee instead of Romney.