Rick Santorum’s withdrawal from the race seems to make Mitt Romney the inevitable Republican presidential nominee. As the former Massachusetts governor turns to the general election, I have a modest proposal for him: Don’t try to win the election. Try to change America instead.

Romney should give up on contorting himself to please voters, for America and the Republican Party desperately need a leader who will put truth above popularity, and honestly discuss the costs of the benefits he promises.

If nominated, he will have our attention for the next seven months, which is a great gift. If he uses his visibility to tell voters only what they want to hear, he loses the ability to shape the nation. He could use the election to promote honest accounting and a culture of responsibility, which would earn him a permanent place in the American pantheon whether he wins in November or not.

He starts as a significant underdog. President Barack Obama has natural political skills, a powerful organization and can claim to have shepherded the U.S. through calamitous times. Intrade.com gives Romney only a 37 percent chance of winning the national election. Unless the most recent jobs report portends a further weakening of the economy, the president will be hard to beat.

High Road

Big gambles, like going for two-point conversions or choosing an unknown Alaskan governor as a running mate, are the right strategy when the status quo means defeat. Romney will need to shake things up; let’s hope he gambles on traveling the high road rather than the low, with appeals to anti-China hysteria and the like. Let’s hope he follows the risky route of Henry Clay and Wendell Willkie, who both preferred being right to being president.

In 1940, Willkie did far more good for the world by losing well than he could have achieved by dishonorably winning the White House. Before Pearl Harbor, there were plenty of America First isolationists, and Willkie could have brought out his base by charging President Franklin D. Roosevelt with war-mongering. Yet, while he occasionally waffled, Willkie generally limited his appeals to isolationism, making it easier for FDR to continue aiding England in its darkest hour, and to challenge Japan. Willkie’s electoral sacrifice probably also helped ensure that America would enter World War II as a more united nation.

Romney can do something similarly noble today, by choosing an election strategy that puts America’s interests ahead of his own. Any reform of our political system, and our society, needs to start with a culture of responsibility -- a broad acceptance that we need to pay for our pleasures. The Bill of Rights didn’t promise us cheap gas or toll-less highways or the right to every new medical innovation at no cost.

Republicans want lower taxes; Democrats want more publicly funded services. Both views can be honorably defended, but it is hard to respect Republicans who promise lower taxes without explaining clearly what spending will be cut, or Democrats who want an ever-expanding public sector, paid for with someone else’s money.

We cannot sensibly decide if we want bigger or smaller government without first acknowledging that lower taxes must eventually mean fewer public services, or that more public activity must eventually impose costs on the private sector.

Romney’s campaign website contains the high-sounding phrase “We have a moral responsibility not to spend more than we take in.” But while his economic plan clearly spells out the tax cuts that will let voters take home more cash, it is woefully lacking in details about who will pay for those lower taxes, beyond imposing block grants for Medicaid. The proposal calls for capping the federal budget at 20 percent of gross domestic product, but contains no discussion of how those funding cuts would materialize.

Ryan Budget

This reticence about spending cuts isn’t limited to Romney. The 2013 blueprint presented by Paul Ryan, the Republican representative from Wisconsin who is chairman of the House Budget Committee, seems so fresh precisely because the U.S. has a surfeit of politicians, on either side of the aisle, who promise benefits without costs. Ryan may cut taxes and spending too much, but at least he has put forward an adult document that tries to grapple with the debt rather than just passing on problems to the next generation.

The Republican Party lost its credibility on fiscal discipline decades ago, but Obama’s vast deficits (justifiable or not) have given his opponents an opportunity to regain the mantle of responsibility. To recapture that role, Romney needs to openly acknowledge that tax cuts only come from meaningful reductions in public services, and make the case that the cuts in services are worth the cuts in taxes.

Once Romney starts to own those service reductions, he will begin to appear more like a leonine leader and less like just another ambitious pol. Maybe, he can even start a fiscal-honesty trend. Medicare costs are the biggest budget buster, but politicians view supporting limitations on public health care as only slightly less career-threatening than expressing sympathy for Iran’s nuclear ambitions. If Medicare must be an open-ended entitlement that gives every citizen the right to the publicly funded purchase of every new medical procedure, then the free market will ensure enough medical innovation to bankrupt the nation.

President Dwight D. Eisenhower must have been palpitating in his grave when Republican leaders started referring to modest attempts at public cost containment as “Death Panels.” Ryan has proposed a brave, but unpopular, plan, to eventually replace Medicare with a voucher system that would limit costs to taxpayers.

Romney’s Plan

At first, Romney noted that “the plan put forward by Congressman Paul Ryan makes important strides in the right direction by keeping the system solvent and introducing market-based dynamics,” but his campaign then followed up with this: “As president, Romney’s own plan will differ, but it will share those objectives.”

If Romney wants to lead, he must risk more by telling more. But leading through honesty goes beyond the budget to the economy as a whole. I share Romney’s view that private entrepreneurs are the wellspring of economic innovation, and I also see much to like in lower taxes and limited regulation. But these policies are no guarantee of economic prosperity, especially for lower-middle-income Americans. A candidate who would lead must ask Americans why they think they are entitled to good jobs at high wages, when there are better-trained workers in China who are willing to work harder for less money.

If Americans expect to be paid more, they must have more human capital -- the formal skills and ephemeral talents that make people productive. If we want our children to be as prosperous as those of the Pacific Rim, then we must put in the same hours teaching core math and science skills.

Our basic economic system is better than any state capitalism alternative, but it cannot ensure that less-skilled Americans will permanently out-earn better-trained international competitors. America needs leaders who will force the country to face its options honestly. Lower taxes mean less public health care. Too little time doing algebra with your children means they will be less prosperous than future competitors in the labor market.

Telling the truth may not get Romney elected, but it should earn him the lasting gratitude of his nation, and that is ultimately far more valuable.

(Edward Glaeser, an economics professor at Harvard University, is a Bloomberg View columnist. He is the author of “Triumph of the City.” The opinions expressed are his own.)

Read more online from Bloomberg View.

Today’s highlights: The View editors on disclosure of the chemicals used in hydraulic fracturing; Ezra Klein on the tax pledges of Republicans and Democrats; Amity Shlaes on how labor laws hurt job creation; Caroline Baum on promoting inflation as the wrong way to cope with debt; Gary Shilling on whether the Federal Reserve will rescue the economy; Doug Skinner on corporate dividend policies; and Robert Bruegmann on why the anti-freeway movement hurts cities.

To contact the writer of this article: Edward Glaeser at eglaeser@harvard.edu.

To contact the editor responsible for this article: Max Berley at mberley@bloomberg.net.