More than one-fifth of non-filers are elderly, a constituency likely to favor Mr. Romney.
The legislation, which adds prescription drug benefits to Medicare, is crucial to the elderly, an important constituency in next year's elections.
In the final weeks of the campaign, Mr. Regalado focused on his core constituency, elderly Hispanics, who appear to have come out strongly in his favor.
But that paled in comparison with his uncomfortable split with his party's leadership over a bill calling for a multibillion-dollar expansion of Medicare to provide low-cost prescription drugs to the elderly, an important constituency for both parties.
Mr. Kerry's focus on the issue came as his campaign began what it called an intense effort to court the elderly, a critical constituency in the election, the day after an independent poll showed that signing the Medicare bill in December had not given the president a lift among older voters.
If the cuts are not reversed, Congress and the administration will face the wrath of two politically potent constituencies, elderly voters and doctors who care for the elderly.
After clashes with entrenched interest groups over education, firehouse closings and other knotty issues, Mayor Michael R. Bloomberg is seeking to bring his business-minded, results-based approach to an especially challenging constituency: the elderly.
He said he knew an elderly woman in his constituency who had come from Poland to the UK in the 1960s and still could not speak a word of English – but he stressed that sometimes there were other forces at play.
Dr Bruce Sizer, a consultant oncologist at nearby Colchester General, says there are 25% more elderly people in the constituency than the national average and that puts pressure on cancer and other healthcare services.
