BOSTON — The Democratic Party called on some of its rising stars and aging liberal lions to present John Kerry's credentials to be president of the United States, sometimes in very personal ways, as the party's four-day national convention reached its halfway point Tuesday night.

From Ted Kennedy, the fourth longest serving U.S. senator in history, to Barack Obama, a young state legislator who is the party's best chance to take a Senate seat from the GOP, they assailed President Bush's performance as commander-in-chief, particularly in the war in Iraq.

They did so by recounting Kerry's heroism as a naval officer commanding a Swift Boat in the Mekong Delta during the Vietnam War and the foreign policy experience he gained during his two decades as a member of the Senate Foreign Relations Committee.

However, in adhering to the "strength and service" themes the Kerry campaign strategist have imposed on the convention, the second night of speeches lacked the political electricity of the opening night, when former President Clinton repeatedly brought the 4,300 delegates to their feet with a pointed series of contrasts between Kerry and Bush.

Still, in a major political coup for the Democrats, Ron Reagan addressed the conventioneers Tuesday night on the importance of federal funding of embryonic stem cell research, saying voters in November face a choice between "the future and the past, between reason and ignorance, between true compassion and mere ideology."

Reagan's father and namesake, the 40th president of the United States, died last month from complications resulting from Alzheimer's disease, a deterioration of the brain which some experts believe can be combated through stem cell research.

"I am here tonight to talk about the issue of research into what may be the greatest medical breakthroughs in our or in any lifetime — the use of embryonic stem cells, cells created using the material of our own bodies — to cure a wide range of fatal and debilitating diseases," Reagan said.

But the most poignant — and anticipated — testimonial on the second night of the party's national convention came from Kerry's wife, Teresa Heinz Kerry, who referred to the combat decorations her husband received during that decades-old divisive military conflict and the lessons he took from it.