Senator McCain moved decisively to the supply-side Tuesday in a strong speech to the National Small Business Summit in Washington, D.C. For investors, small-business owner-operators, and the vast majority of middle-class Americans who go to work every day and are concerned about Mr. McCain’s tax vision, this speech is good news. Big Mac is the taxpayer-friendly candidate.

The Republican candidate for president embraced low-tax-rate incentives to grow the economy, promising a combination of pro-growth tax reform and simplification along with significant spending restraint. He has called himself a foot soldier in the Reagan revolution. This tax speech clinches it.

Mr. McCain pledged to keep taxes low for families and employers, putting himself squarely in Ronald Reagan’s camp and offering to extend the long prosperity wave started by the Gipper more than 25 years ago. In contrast, Mr. McCain charged Senator Obama — who gave his economic speech on Monday — with proposing the single-biggest tax hike in the entire post-World War II period.

Mr. McCain asserted that “no matter which of us wins in November, there will be change in Washington. The question is what kind of change?” Mr. Obama says a McCain victory will hand President Bush a third term. Mr. McCain says an Obama victory gives Jimmy Carter a second term.

I think Mr. McCain gets it right.

Getting down to specifics, Mr. McCain said he would maintain the low income and investment tax rates put in place by Mr. Bush. He singled out the need to keep the capital-gains tax rate at a low 15%, so that businesses will have the investment necessary to expand jobs, productivity, and real wages.

Completely unlike Mr. Obama, Mr. McCain is saying you can’t have capitalism without capital. And he recognizes that investors must have high after-tax returns in order to take risks and fuel entrepreneurial activity. On this point, think high-risk energy technologies for clean coal, natural gas, oil shale, nuclear, and cellulosic power.

Mr. McCain repeated his plan to reduce the corporate tax rate to 25% from 35%. This could be his single most important tax reform. Not only will it enhance America’s global competitiveness, since we have the second highest corporate tax among large countries. But a number of studies show that roughly 70% of the benefits from a lower corporate tax will flow to the workforce in the form of higher real wages and more jobs.

Mr. McCain also pledged to keep the estate tax low to reward family businesses. Overall, he would seek a flatter and simpler tax system, probably modeled on Rep. Paul Ryan’s idea of two rates of 25% and 15%. Mr. McCain also discussed several middle-class tax cuts, such as doubling the child tax exemption and phasing out the alternative minimum tax. For businesses, Mr. McCain added a first-year cash-expensing provision for the write-off of new equipment and technology.

Mr. McCain coupled all this with a pledge to veto earmarks and pork-barrel spending. He held out as an example the outrageous $300 billion farm bill that drew Mr. Obama’s vote. Mr. McCain would go after corporate welfare and freeze discretionary spending outside of the military. And he made an especially strong case for the free-trade policies that have been so important to American economic growth.

The McCain-Obama contrast couldn’t be more stark. Mr. Obama wants to use the tax system to redistribute income and wealth, not to grow the economy. He constantly talks about rewarding work over wealth. This is pure class warfare.

Mr. Obama doesn’t seem to understand that our nation was founded on the principle of equality of opportunity, and that private enterprise, not government, is the main economic driver. Mr. Obama intensely dislikes businesses. He would repeal all the Bush tax cuts and raise the corporate tax.

Mr. Obama talks about the need for bottom-up economic growth. But this is a canard. He’s pure top-down when it comes to big-spending government programs.

Mr. Obama singled out the ownership society, calling it a “worn dogma.” In fact he misjudges modern America, which is dominated today by 100 million investors, 25 million small-business owners, nearly 70 million homeowners, and roughly 140 million people who go to work everyday in the corporate world.

Mr. Obama opposes free trade. And though he has tried to hedge his bet on this point, it will never sell in this YouTube election.

Earlier in the campaign, he became the candidate of 1970s scarcity and limits when he asserted that “we can’t drive our SUVs and eat as much as we want and keep our homes on, you know, 72 degrees Fahrenheit at all times, and then just expect that every other country is going to say okay.”

Ironically, it’s Mr. McCain who is saying “Yes we can.” We can grow. We can prosper. We can be confident about the future. He’s saying that with the right economic policies, America’s outlook will know no bounds.

Mr. Kudlow is host of CNBC’s “Kudlow & Company.” © 2008 Creators Syndicate, Inc.