MARYLAND IS the latest state to extend college tuition breaks to undocumented immigrants who graduate from state high schools, provide tax returns going back five years, prove their academic mettle by completing two years of study in a community college and, for men, register for the draft.

The measure is a tough, fair and sensible way to help make college affordable for students who grew up in Maryland but, often through no fault of their own, lack legal status in this country. Beyond helping them, it would help Maryland by providing credentials to talented young people who would be prepared to contribute to the state’s economy.

But the legislation, signed into law this week by Democratic Gov. Martin O’Malley, is under attack by anti-illegal-immigrant activists. Brandishing slogans about respect for the law and the misuse of public funds, the activists want to make life so impossible for undocumented immigrants that they will somehow be forced to go “home.” Never mind that Maryland is the only home that many of these students, thoroughly American in speech, habits, culture and allegiance, know or remember.

The activists have launched a petition drive to block the law from taking effect this year by collecting about 58,000 valid signatures to put it on the ballot in 2012.

The leader of the petition drive is Pat McDonough, a Baltimore County lawmaker who was among 55 Republicans to vote as a bloc against the legislation, known as the Dream Act, last month. Mr. McDonough is a radio talk show personality whose past crusades have included enshrining English as Maryland’s official language and promoting ownership of stun guns and Tasers. His record of success in the General Assembly is almost nil; the legislature has passed just two bills of the more than 50 he’s introduced since being elected to the House of Delegates in 2002. He refers to Annapolis as “Wackoville” and the legislature as the “General Asylum.”

Mr. McDonough insists that tuition breaks for undocumented immigrants will cost Marylanders “hundreds of millions of dollars” in lost tuition revenue; in fact, most estimates are considerably lower than that. He says undocumented Maryland students should pay the out-of-state rate if they want to attend college. The reality is that many will not be able to afford it.

The bottom line for Mr. McDonough, as for many Republicans, is that illegal immigrants can and should be made to leave the country, and that federal, state and local governments can hasten that process by taking legislative and administrative steps that make life impossible for them.

This is fantasy, of course. Eleven million undocumented immigrants are in America, 7 million of them in the workforce; many have been here a long time and are deeply interwoven in the fabric of their communities. The idea that they can somehow be made to disappear — “attrited,” in Mr. McDonough’s euphemism — is a daydream. It won’t fly with businesses, industries and citizens that need and have come to rely on undocumented workers and residents.

In following at least 10 other states in enacting some version of the Dream Act, Maryland opened a door to youngsters who hope for a better future, like generations of immigrants before them. If that door is slammed, Maryland will shortchange its own future by blocking those residents from fulfilling their potential.