Both political parties deserve blame for the spending spree that's put America in a fiscal ditch. President George W. Bush was a big spender and President Obama has compounded the damage with his stimulus spending and other programs.

But the era of bipartisan big government may have come to an end. Largely thanks to Rep. Paul Ryan and the fiscal blueprint he prepared as chairman of the House Budget Committee earlier this year, the GOP has begun climbing back on the wagon of fiscal sobriety and has shown at least some willingness to restrain the growth of government.

The Ryan budget has generated considerable controversy in Washington, and it will become even more of an issue now that Mr. Ryan is Mitt Romney's running mate. So it's an appropriate time to analyze the plan and consider what it would mean for America.

The most important headline about the Ryan budget is that it limits the growth rate of federal spending, with outlays increasing by an average of 3.1% annually over the next 10 years. If spending is left on autopilot, by contrast, it would grow by 4.3% (or nearly 39% faster). If President Obama is re-elected, the burden of spending presumably will climb more rapidly.

This comes as a surprise to many people since the press is filled with stories about the Ryan budget imposing trillions of dollars of "savage" and "draconian" spending cuts. All of these stories, however, are based on Washington's misleading budget process that automatically assumes an ever-expanding government. The 4.3% "base line" increase is the benchmark for measuring "cuts" — even though spending is rising rather than falling, and it's only the rate of spending growth that is being slowed.

Even limiting spending so it grows by 3.1% per year, as Mr. Ryan proposes, quickly leads to less red ink. This is because federal tax revenues are projected by the House Budget Committee to increase 6.6% annually over the next 10 years if the House budget is approved (and this assumes the Bush tax cuts are made permanent). Since revenues would climb more than twice as fast as spending, the deficit would drop to about 1% of gross domestic product by the end of the 10-year budget window.

To balance the budget within 10 years would require that outlays grow by about 2% each year. Spending in the Ryan budget means the federal budget reaches balance in 2040. There are many who would prefer that the deficit come down more quickly, but from a jobs and growth perspective, it isn't the deficit that matters.

Rather, what matters for prosperity and living standards is the degree to which labor and capital are used productively. This is why policy makers should focus on reducing the burden of government spending as a share of GDP — leaving more resources in the private economy.

The simple way of making this happen is to follow what I've been calling the golden rule of good fiscal policy: The private sector should grow faster than the government. This is what happens with the Ryan budget. The Congressional Budget Office expects nominal economic output (before inflation) to grow about 5% each year over the next decade. So if federal spending grows 3.1% annually, the burden of federal spending slowly shrinks as a share of GDP.

According to the House Budget Committee, the federal budget would consume slightly less than 20% of economic output if the Ryan budget remained in place for 10 years. This would be remarkable progress considering that the federal government is now consuming 24% of GDP vs. Mr. Clinton's 18.2% in 2001. If Paul Ryan's policies are social Darwinism, as Mr. Obama and his allies allege, one can only speculate where Bill Clinton ranks in their estimation.

Spending restraint also creates more leeway for good tax policy. Regardless of what you think about deficits, the political reality is that it is difficult to lower tax rates if government borrowing remains at high or rising levels. If deficit spending continues at current levels, then higher tax rates are almost sure to follow. And higher tax rates can't create an environment conducive to more investment and jobs.

The Ryan budget avoids this unpleasant outcome by addressing the problem of excessive government spending. This makes it possible to extend the 2001 and 2003 tax-rate reductions. It also clears the way for other pro-growth reforms, such as Gov. Romney's proposed across-the-board 20% income tax cut, a more competitive 25% corporate tax rate, and less double-taxation of dividends and capital gains.

One of the best features of the Ryan budget is that he reforms the two big health entitlements instead of simply trying to save money. Medicaid gets block-granted to the states, building on the success of welfare reform in the 1990s. And Medicare is modernized by creating a premium-support option for people retiring in 2022 and beyond.

This is much better than the traditional Beltway approach of trying to save money with price controls on health-care providers and means testing on health-care consumers. Price controls are notoriously ineffective — because health-care providers adapt by ordering more tests and procedures — and politically unsustainable due to lobbying pressure. Means testing imposes an indirect penalty on people who save and invest during their working years. That should be a nonstarter for a political party that seeks to encourage productive behavior and discourage dependency.

But good entitlement policy also is a godsend for taxpayers, particularly in the long run. Without reform, the burden of federal spending will jump to 35% of GDP by 2040, compared to 18.75% of output under the Ryan budget.

Assuming the GOP ticket prevails in November, Mitt Romney will make the big decisions on fiscal policy. But there is no escaping the fiscal math. If Mr. Romney intends to keep his no-tax-hike promise, he has to restrain the growth of spending. This doesn't mean he has to go with every detail of the Ryan budget — but it's certainly a good place to start.