WASHINGTON (CNN) -- Former New York City Mayor Rudy Giuliani once said that a flat income tax "would be a terrible mistake for urban areas," but the presidential hopeful now is open to the idea.

Giuliani made his critical comments about the flat tax during an appearance on CNN's Capital Gang in 1996, the same year when its biggest cheerleader, Steve Forbes, was seeking the GOP presidential nomination. Forbes, the editor-in-chief of the magazine that bears his name, endorsed the former mayor this week and will serve as a senior policy advisor and national co-chair of the campaign.

When asked about the flat tax this week, Giuliani said that if the nation was back at the point where the income tax was being structured then it "would make a ... lot of sense.

"It would be a lot simpler," Giuliani said at a news conference on Wednesday. "It would be a lot easier. It would probably bring in a lot more revenue and it would not have some of the burdens on the economy that the massive tax code has on the economy."

But Giuliani hedged that he is not sure if it is doable at this point.

"Whether you can get there given where our economy is right now, or you can't, ah, is a different story," he said. "What, where you can get is massive tax simplification, which I think really happened and Steve would be more of an expert on this, during the Reagan administration."