Contrary to Democrats’ assertions that the math in GOP presidential nominee Mitt Romney’s budget plan doesn’t add up, former Florida Gov. Jeb Bush voiced confidence Friday that Romney’s plan will work.

The key, Bush said, is boosting economic growth to 4 percent — about twice the rate it is currently expanding.

Romney has proposed cutting income tax rates across the board by 20 percent. His statement that he can do this while still generating the revenues needed to run the government has been widely criticized by pundits as too vague.

But in Romney’s speech on the economy Friday, he emphasized the need to return the United States to a 4 percent annual rate of economic growth, in order to get the budget back on an even keel. The Obama administration has been running budget deficits of over $1 trillion per year.

In his exclusive Newsmax TV interview Friday, Bush echoed the importance of renewed economic growth.

“There’s no amount of expropriation of people’s assets or income that would generate as much money as an economy growing at 4 percent per year,” Bush said. “If we had 10 years of sustained growth that is, say, 2 percent higher than we have today, in the 10th year we’d create a Germany in terms of additional economic activity. That’s the way that Gov. Romney’s proposing this.”

Simplifying the tax code and lowering rates, Bush said, will generate greater economic activity and investment.

“To put it into prospective,” he said, “we have 1.2 trillion dollars of what are called tax expenditures. Those are deductions and credits and all sorts of things where people get in line to get their piece of the tax pie, if you will.