In announcing Sen. John Edwards (N.C.) as his vice presidential running mate yesterday, Sen. John F. Kerry added one of the party's brightest stars and most talented campaigners to the Democratic ticket, but he left himself open to criticism that he had passed up candidates with far more experience for someone who lacks a significant legislative or executive record.

The selection of a vice president often tells as much about a candidate and his approach to a presidential race as any other decision of the campaign. The choice of Edwards suggests that Kerry is secure enough to have picked a running mate widely judged to be the more effective campaigner and confident enough not to fear comparisons.

The decision also points to the Massachusetts senator's belief that his own foreign policy and national security credentials -- Vietnam War veteran and longtime member of the Senate Foreign Relations Committee -- will be enough to reassure voters of the Democrats' capacity to protect the country in a era of terrorism. With Edwards, he adds an eloquent voice for an entirely different set of issues that Democrats want to push into the forefront of the campaign, including anxiety over the economy and worries about the rising cost of health care.

Kerry is gambling that Edwards's campaign skills will count more than credentials in the next four months, that the excitement Edwards helps to generate will have a more profound impact on voters than the absence of any particular achievements in the Senate.

Yesterday's announcement helped frame the election against President Bush and Vice President Cheney, with the Democrats determined to make the campaign a choice between change and a status quo that many Americans say is unacceptable, according to polls.

Republicans were quick to suggest that the direction the Democrats want to take the country is much further to the left than the voters will tolerate and that the new ticket symbolizes the leftward drift of the party since President Bill Clinton left office. "There is a brand on this ticket now as the most liberal ticket ever," said Matthew Dowd, chief strategist of the Bush-Cheney campaign.

Democrats believe the addition of Edwards gives the party the opportunity to put North Carolina into competition in November, along with another southern state or two. There is no guarantee that Edwards can deliver states for Kerry, but his presence on the ticket could boost the chances of Democratic Senate candidates in the South, a region where Kerry's northeastern roots do not play well.

Democrats also see Edwards, who was reared in a small mill town in North Carolina, as complementing Kerry in other ways, particularly his potential appeal to small-town and rural voters in midwestern battlegrounds where the Democrats fared badly four years ago.

All of that, however, is a tall order to put on the shoulders of a vice presidential candidate, and Republicans believe Democrats will find nothing but disappointment as they pursue those assumptions.

In the end, the choice of a vice president rarely determines the outcome of an election, as George H.W. Bush's selection of Dan Quayle proved in 1988. But that does not diminish the significance of the choice, both from the way a presidential nominee approaches the decision to the initial impact it has on a political party and the voters.

Judged by those criteria, Kerry won high marks yesterday, even privately by some Republicans. Edwards was the overwhelming favorite of the party's rank-and-file voters and the announcement that he had been chosen sent a jolt of energy and enthusiasm through the party that had been missing in the Kerry campaign.

Democrats hope their ticket will be able to ride that enthusiasm through the national convention in Boston at the end of the month to a clear lead in the polls, as Clinton was able to do when he picked Al Gore as his running mate in 1992. Republicans acknowledge that the president and Cheney probably will fall well behind by early August, having sent out a memo before the announcement predicting a Kerry bounce in the polls.

But their assessment is that the Democratic ticket will not play well over time as voters begin to weigh their choices in the fall and as they size Edwards up against Cheney. "I think in the end, it's going to play out better on our side," said Vin Weber, a former House member and an official in Bush's reelection campaign.

Weber predicted that the course of Edwards's vice presidential candidacy will encompass the overall presidential campaign. "If voters go to the polls believing that America is at war, with terrorism and at war in Iraq, I believe they're going to reelect President Bush," he said. "If they go to the polls thinking about other things, it's going to be very close."

In Weber's analysis, if terrorism and national security dominate the mind of the electorate, "No amount of smiling and charisma will make up for the fact that Kerry's chosen a vice presidential candidate who does not really have vice presidential credentials, and it will hurt the ticket."

Not surprisingly, Democrats sharply disagreed. "I think the most important dimension is fresh start, that we offer the country a fresh start," said Democratic strategist Mandy Grunwald. "I think people have made a decision they don't want to continue in Bush's direction but have been unsure what direction Kerry will offer, and this feels new and energetic and that's incredibly important."

Democratic pollster Peter D. Hart said Edwards provides Kerry with a direct link to voters, someone who can prompt voters to relate to the Democratic ticket with a "two Americas" message that he said is more in tune with the electorate than anything offered by any other candidate.

"Because Kerry has been a United States senator, he crossed the bar on the experience factor earlier than other previous challengers," Hart said. "There is no doubt about Kerry's ability to be president. So if you have to give up something to get the linkage, that is an easy one to give up."

Kerry advisers were peppered with questions to explain how Edwards fit one of the five criteria that the candidate had set out for his vice presidential selection team, headed by Washington businessman and Democratic veteran James Johnson.

The last of them, according to a campaign document, said, "Fifth, and most important, the candidate had to be ready, at any moment, to assume the awesome responsibility of president."

Asked about Edwards's lack of experience, campaign manager Mary Beth Cahill said, "Senator Edwards has been a leader through his life, and he understands the concerns and desires about the middle class and those who want to be in the middle class better than anyone in politics."

Saying the race is not only about national security and defense but also about financing college education, paying for health care and getting a good job, she added, "He has talked about those in every state of the country, and he will bring those into the debate."

Democrats also noted that Bush had no more experience in national security and foreign policy when he ran four years ago, although the world has changed dramatically since as a result of the terrorist attacks of Sept. 11, 2001.

Republicans called the choice of Edwards a political decision, but some privately said it was smart politics on Kerry's part, that the presumptive nominee had looked for the person who could help him most to win the election. In Edwards he found a running mate who they said could humanize the ticket and who, according to exit polls during the Democratic primaries, generally did better with voters the more they got to know him.

Four years ago, when Gore was considering Edwards as his running mate, one pro-Edwards adviser said the freshman senator might not be the best choice initially because he was so little known nationally and so untested, but that by October his campaign skills would prove to be a significant help in closely fought states.

This time Edwards is clearly the popular choice at the front end of the campaign. But voters may have different calculations this year than they did four years ago, and the challenge for Edwards and Kerry is to prove that he has not only the campaign skills to energize Democrats but also the intangibles necessary to convince voters that the Democratic ticket is prepared for all contingencies, domestic and foreign.

Sen. John F. Kerry's pick of Sen. John Edwards as a running mate is expected to boost the ticket's profile in the South.