Democratic presidential candidate John Kerry (search) canceled a campaign swing to New Mexico and returned to the Capitol on Tuesday to vote on a Senate measure requiring mandatory funding of health care for military veterans, a constituency he has courted since the beginning of his bid.

Campaigning for president has made Kerry a rare figure in the Senate for most of the year. He has participated in just 17 of 135 votes since January, according to an Associated Press tally. However, Kerry said the veterans health care amendment to the fiscal 2005 defense authorization bill drew him back to Washington.

"It's a particular issue that's been very critical to me," Kerry told reporters as he walked into the Capitol. "It's central to something I want to get done."

Asked if he was meeting with anyone he is considering for a running mate, Kerry said, "I'm going to have lots of meetings today." When he walked past reporters staking out his office in case any potential candidates came to see him, Kerry told them, "You're going to be disappointed."

On Tuesday, the campaign unveiled a 30-second television ad about health care that will run on local media markets in 13 of the 20 states where Kerry is on the air. Without naming President Bush, the ad seeks to contrast health care under the Republican's administration with Kerry's proposal.

Kerry claims that $350 billion of the $1.5 trillion the United States spends each year on health care is administrative overhead. His plan, he says, "will save literally billions of dollars in health care costs in America by becoming more streamlined and more efficient."

Steve Schmidt, a Bush campaign spokesman, described Kerry's health care plan as "a giant government takeover of the American health care system, which will result in more paperwork, more bureaucracy and higher costs."

On the issue of veterans, Kerry, who served in the Navy during the Vietnam War, rarely gives a speech in which he doesn't call for better benefits.

Bush opposes mandatory veterans health care funding, with his campaign advisers arguing that mandatory funding would put all veterans in the federally funded health care system, even those who have health coverage elsewhere, and would reduce the amount available to cover veterans who need the care most.

The Bush administration has increased benefits, veterans' enrollment in VA health care and spending overall for that department. But the administration has prohibited new enrollments of veterans with the highest earnings unless their health problems are related to their military service.

The Kerry campaign says under the administration's policy, about 500,000 veterans are scheduled to be left out of the VA health system.

Funding for veterans health care was $26.4 billion this year, according to the Kerry campaign. The amendment that Kerry is returning to vote for would increase funding next year by 30 percent, or nearly $8 billion, to cover all 26 million veterans. The amount would rise in later years to cover new veterans coming into the system and the rising cost of their care.

Kerry had planned to fly from Denver to New Mexico Monday night, then deliver a speech describing his plan for federal investments in science and technology on Tuesday morning in Albuquerque. But about an hour before Kerry was scheduled to leave Denver, his campaign announced that he was flying back to Washington instead.

Massachusetts Republican Gov. Mitt Romney and Lt. Gov. Kerry Healey last week called on Kerry to resign from the Senate because he's missed so many votes, but Kerry said he's serving his constituents well by running for president.