New York ? When John Kerry and Hillary Rodham Clinton took the stage together Wednesday at the City College of New York, some students saw a winning combination.

“I want to know,” one demanded, “who is going to be your running mate?”

“I’ll just tell you,” Kerry joked. “We’ll keep it a secret in this room.”

A few weren’t shy about what they wanted to hear, yelling, “Hillary! Hillary!”

But the Massachusetts senator and his New York colleague simply smiled and moved on. Kerry revealed only that the selection process, which he described as personal, would be completed “between now and the convention in Boston,” which begins July 26.

The Democratic presidential candidate has done little to illuminate his thoughts on what he’s looking for in a running mate. But whether he picks the former first lady or not, she and former President Bill Clinton will be major power brokers in this year’s election.

They remain among the most popular Democrats in the country, and Kerry is counting on their support to raise campaign cash and get hard-core Democrats to the polls. But their help is complicated by Clinton’s past scandals and Mrs. Clinton’s potential White House ambitions.

Mrs. Clinton, who has said she was not interested in the No. 2 spot, told students at this school in Harlem that they could depend on Kerry.

Democratic presidential candidate Sen. John Kerry , D-Mass., left, embraces U.S. Sen. and former first lady Hillary Rodham Clinton during a rally at City College in Harlem, New York. The pair campaigned there Wednesday.

“John Kerry has never let his friends down, his crew down, his constituents down or his country down,” she said. “He is ready, willing and able to lift our country up.”

The City College visit, which preceded a major fund-raiser Wednesday night in Manhattan, was the most recent stop on Kerry’s weeklong “Change Starts With U” campus tour. Kerry acknowledged that he has to work to engage a demographic that has become increasingly disaffected.

“I understand why,” he said. “Because you’re tired of being disappointed.”

Hitting upon themes that harked back to Kerry’s political hero, John F. Kennedy, the candidate called upon students to serve their country.

“We need you back,” he said. “I want you to please understand that this race is a race of empowerment.”

Kerry announced a tuition assistance plan that would reward community service. Dubbed the “Compact with the Next Generation,” the program would provide free in-state tuition at public universities to students who spend two years in jobs such as teaching, tutoring or building affordable housing.