Final answer:
The AARP's support was critical to the passage of the Medicare Prescription Drug and Modernization Act of 2003 due to their powerful lobbying efforts and strategic decision to back the plan with a higher likelihood of passing.
Step-by-step explanation:
The passage of the controversial prescription drug program for the elderly in 2003, known as the Medicare Prescription Drug and Modernization Act of 2003, was heavily influenced by the support of a particular lobbying group. The correct answer to which group's support was critical is AARP (formerly the American Association of Retired Persons). AARP is well-known for advocating for the interests of senior citizens, particularly regarding healthcare costs and the safety of Social Security pension payments. In 2002, while Democrats and Republicans had differing approaches to Medicare's expansion, AARP sided with the Republicans' plan.
This bipartisan support from AARP was instrumental in convincing moderate Democrats to vote in favor of the bill, thereby ensuring its passage. AARP's preference for a plan that was more likely to pass, rather than holding out for an ideal but potentially unachievable option, demonstrates the organization's strategic lobbying efforts on behalf of seniors.