The Department of Education on Wednesday tightened its regulation of for-profit colleges and other vocational programs that get billions of dollars in federal aid but leave many students with crushing debt and credentials worth little on the job market.

Under the new rules, programs would lose their eligibility to dispense federal student aid — and as a practical matter, be shut down — if, over the next four years, their graduates fail to meet new benchmarks for loan repayment and ratio of debt to income. But amid intense lobbying by the for-profit college industry and pressure from Republican lawmakers, the department significantly eased the rules from an earlier draft: officials said, for example, that no program would lose eligibility until 2015.

“We believe that very few programs will be forcibly closed by our standards,” Secretary of Education Arne Duncan said. “We want to give people a chance to reform. As a country, we need this sector to succeed. This is not about ‘gotcha.’ ”

These rules, which try to define how such programs prepare students for “gainful employment,” have been the hardest-fought issue in the debate over exploitive and fraudulent practices in the industry. The colleges and their allies spent $12 million lobbying against the rules since the start of 2010, and this spring, the House passed a budget amendment that would have blocked the department’s work on them. The rules were supposed to be issued last summer, but were delayed after the Education Department received a record 90,000 comments on its draft proposal.