New York Mayor Bill de Blasio, who vowed to become national leader for progressives, took his campaign for higher taxes on the rich to America’s heartland and the home of the first presidential test of 2016.

De Blasio, 53, brought the same message to Des Moines, Iowa, that he delivered to New Yorkers a little more than a year ago, when he became the first Democrat in 20 years to run the largest U.S. city. He says income inequality is the defining issue of our time.

“It’s clear that the wealthy among us could sustain higher taxes,” de Blasio said during remarks Thursday to a crowd of about 60 in Drake University’s library, where he was a guest of former U.S. Senator Tom Harkin and the Harkin Institute for Policy and Citizen Engagement. “If we accept the status quo, and if we accept it in particular because we think it’s politically untenable to confront it, we will put ourselves in danger.”

He cited Lloyd Blankfein, chief executive officer of Goldman Sachs Group Inc., who said last year that inequality was “destabilizing.” He also quoted billionaire Warren Buffett, who said of successful investors, “potential taxes have never scared them off.”

De Blasio’s remarks came amid a Midwest swing that included a stop in Nebraska on Wednesday. He arrived in Iowa the same week as former Secretary of State Hillary Clinton, the newly announced candidate and presumptive frontrunner for the Democratic presidential nomination.

De Blasio managed the former first lady’s successful 2000 bid to become a U.S. senator from New York, and in 1997 he worked for the U.S. Department of Housing and Urban Development in her husband’s administration.

No Endorsement

New York’s tabloids made front-page news out of de Blasio’s refusal to endorse Clinton on April 12, the same day she declared that she was in the race. The mayor said he would wait until she supports policies consistent with his agenda.

Clinton joined about nine others as Harkin’s dinner guest at his home Wednesday night, the former Iowa senator said. They didn’t discuss the mayor’s non-endorsement, he told reporters.

“I said I was going to be with Bill de Blasio today and she said, ‘I love Bill de Blasio,’” Harkin said. “She was very high on Bill.”