With Senator Thompson’s official entry into the presidential race, Senator Clinton needs to watch out. Demographics, policies, and personality make Mr. Thompson a formidable opponent, and voters will take him seriously.

Since 1964, all winning presidential tickets have been led by a Southerner or a Westerner, and Mr. Thompson, from Tennessee, fits the profile of a successful candidate. By successful I mean, the candidate capable of beating the leading Democrat, Hillary Clinton.

Mr. Thompson has a potential solid base of Southern support, a base that the other candidates will have a hard time attracting and that the winner may need.

Mrs. Clinton has posted on her presidential campaign Web site a list of “10 reasons to support Hillary Clinton for president and help make history.” Most of these reasons are, in fact, a reason to support Mr. Thompson.

First on Mrs. Clinton’s list is ending the war in Iraq. Mr. Thompson doesn’t simply want to end the war in Iraq, he wants to win the war in Iraq. There’s a big difference, and most voters want to win, too.

Mrs. Clinton’s second priority is to achieve universal, affordable health care, which she believes requires moving towards a single-payer system.

Her proposal seems eerily similar to her 1994 health care plan which did not resonate with voters. Then as now, Mrs. Clinton does not explain how taxpayers through the government will pay for new health care plans.

In contrast, Mr. Thompson is looking for ways to increase the choice and portability of health insurance plans, and detach them from employers, so that people don’t need a large employer to have health insurance. Moreover, they won’t lose their health care when they change jobs.

Mrs. Clinton’s third reason to support her is that she will create “good jobs for middle-class Americans with the right investments in modern infrastructure.”

In that vein, she wants government-mandated clean technology, with the goal of reducing global warming and American dependence on foreign oil. Mrs. Clinton does not explain how taxpayers through the government will pay for new energy or technology policies.

This is diametrically opposed to Mr. Thompson’s philosophy. He believes in letting employers create jobs based on what works best, not on government-mandated technologies.

The government doesn’t have the knowledge or the budget for massive infrastructure projects, nor does the government know what is the “right” investment and which technology is sufficiently “modern.”

The fourth reason of Mrs. Clinton is “to provide world-class education, from universal pre-kindergarten to affordable college for all.” Mrs. Clinton does not explain how taxpayers through the government will pay for new federal education mandates.

Mr. Thompson’s record has been focused on choice in education, with people being able to choose the schools that are best for them. Many state and local governments can’t even support the schools they have, without adding a federal mandate for pre-kindergarten. Mrs. Clinton wants “to return to fiscal responsibility, move back toward a balanced budget, and safeguard Social Security and Medicare for future generations.” The rhetoric sounds great, but how fiscally responsible can the public consider a candidate who proposes new federal programs and mandates such as those trumpeted by Mrs. Clinton at her Web site? The government can pay for these costly programs only by cutting existing programs, expanding the deficit, or raising taxes.

Rather than tax hikes, Mr. Thompson believes that America needs fundamental tax reform, and he plans to announce a more efficient tax system that favors savings over consumption. The key is lowering the burden of taxation, to allow people to keep more of their own money.

Mr. Thompson is not an ideologue who schemes to eliminate vast arrays of government programs. Rather, he seeks to make existing government programs more efficient.

For the tens of millions of Americans who frequently deal with such federal programs as Medicare, Medicaid, and Social Security, greater efficiency is a must.

Mr. Thompson shares that common sense view. He also recognizes that these programs are on a deficit path now, and need to be reformed, rather than safeguarded.

Mrs. Clinton has grand ideas and often sees solutions in assembling the best and brightest in Washington. That may be the right approach to some problems. But most of the business of government is local.

Mr. Thompson believes in keeping government decisions localized, such as here in New York City, as much as possible. When government programs are operated at the state level, state and local governments can exercise maximum influence over funds and work out where they are needed. Mr. Thompson is not a career politician, and he is not in the race to crown a lengthy political career. He’s in the race because he thinks his solutions to the country’s problems are the right ones. The wide breadth of experience he has developed outside the political arena, and his friendships with those on both sides of the aisle, would serve him in good stead as president.

Mrs. Clinton and Mr. Thompson both have impressive resumes and a clear grasp of the major issues facing the country.

They differ on how to address those issues, and Mrs. Clinton’s fascination with the glitterati of Washington decisions funded by Washington taxes may not serve New York and America well. Mr. Thompson’s entry in the race will encourage a realistic debate.

Ms. Furchtgott-Roth, former chief economist at the U.S. Department of Labor, is a senior fellow at the Hudson Institute.