Home foreclosures have been a major piece of the nation's economic problems, and President Obama's plan is an earnest attempt to keep financially stretched people in their homes. The housing crisis hits home for everyone, from the single mother out on the curb to the family that can still dutifully write mortgage payments despite shrinking paychecks. President Obama's plan to pump $275 billion into decreasing foreclosures may not be precisely the right prescription. But it is medicine and it's badly needed. The proposal arrives with plenty of questions, chief among them: How to do you design a mortgage rescue program that doesn't punish people who have been responsibly doing the right thing, but is broad enough to have a significant effect on the spreading housing crisis? Getting that balance right will be tricky. Mr. Obama's plan is, at the very least, a start. The subprime crisis and foreclosure glut have been leading causes of the current economic dive. For most people, a house is the single largest investment in a lifetime. Protecting that nest egg will be to everyone's benefit. The centerpiece of the President's plan is a $75 billion investment -- drawn from the financial industry bailout money approved by Congress -- that would go directly to keeping homeowners in their houses. A portion would allow those without enough equity to refinance, affecting as many as 5 million people. An owner would be eligible provided his or her mortgage does not exceed 105 percent of current property value. Currently, one in four people nationally is underwater on a mortgage, meaning they owe more than their house is worth, the result of plummeting home values. A second component, affecting about 4 million people on the verge of foreclosure, would provide incentives to banks to alter the terms of loans to make them more affordable. The goal would be to reduce monthly mortgage payments to 31 percent of a homeowner's income. The last piece of the package would seek to increase credit available for loans by giving $200 billion more to Fannie Mae and Freddie Mac. In introducing the plan, Mr. Obama made it clear that he wanted to carefully tailor the help being offered. "The plan I'm announcing focuses on rescuing families who have played by the rules and acted responsibly," Mr. Obama said. "It will not rescue the unscrupulous or irresponsible by throwing good taxpayer money after bad loans." That's the task -- separating the good from the bad and doing so effectively. The Obama administration is working on criteria for lenders in evaluating applicants for this assistance. Loan modifications would apply only to people for whom the home in question is a primary residence. No vacation homes or investment properties would be allowed. Those criteria must be rigidly defined and applied, or this bailout will be funneled in the wrong direction. One looming question is whether the efforts to help people whose mortgages are underwater will be sufficient to reach a broad swath of homeowners. Many householders are so far beneath the sea already that they passed the 105 percent mark leagues ago. That 105 percent number will have to grow, or the pool of qualified applicants will be too small to make any kind of difference. The country could face another big round of mortgage defaults by year's end as the recession deepens. Mr. Obama's plan is an attempt to get a handle on that growing problem. To the extent that it can help us find a floor for housing values, the proposal will keep all of us above ground.