Front-runners Hillary Clinton and Barack Obama held their own in Democrats' latest presidential debate, an event dominated by the questions about them that have come to define the party's contest: Is she too divisive, and he too inexperienced, to be elected and &

if elected &

to govern effectively?

The eight-candidate face-off, televised on ABC's Sunday show "This Week," was the first held in Iowa, whose party caucuses begin the 2008 nominating process. Host George Stephanopoulos opened with new Iowa poll results that set the tone: Sens. Obama of Illinois and Clinton of New York, along with former North Carolina Sen. John Edwards, are in a dead heat, each with support from roughly a quarter of likely Democratic caucus-goers, while the rest are far back.

Clinton is significantly ahead of all rivals in national polls, but the closeness of the top three in Iowa helps explain the attacks they have mounted lately as they jockey for advantage. Likewise, the dark horses have begun taking shots at the front-runners to try to break through.

From the opening question, Obama endured a rehash of recent criticisms from Sens. Clinton, Chris Dodd of Connecticut and Joe Biden of Delaware that some of his foreign-policy positions were naive, even dangerous.

He first countered the charge with humor, saying that to prepare for the debate, "I rode in the bumper cars at the [Iowa] state fair." More seriously, Obama said his positions &

on dealing more openly with foreign adversaries, ruling out nuclear weapons against al Qaeda, or potentially invading Pakistan to get Osama bin Laden &

aren't much different from the other Democrats' stances. He called their criticisms "political maneuvering."

Clinton stood by her contention that "a president should not give away the bargaining chip of a personal meeting with any leader, unless you know what you're going to get out of that." She and Dodd and Biden agreed that the U.S. mustn't do anything in Pakistan to further jeopardize President Pervez Musharraf, whose country has nuclear weapons.

In Clinton's turn on the defensive, she had to explain why Obama was wrong to rule out nuclear weapons against al Qaeda when she once ruled them out against Iran. She said that while Obama was speaking of a hypothetical case, her comment was "a brushback" to actual administration provocations against Iran.

Obama retorted: "It is not hypothetical that al Qaeda has established base camps in the hills between Afghanistan and Pakistan." He added, "No military expert would advise that we use nuclear weapons to deal with them, but we do have to deal with that problem."

Edwards first seemed to support Obama, with a dig at Clinton: "It's not shocking that people who have been in Washington a long time criticize him when he comes along and expresses his view." But then he tweaked Obama, saying that hypothetical talk about nuclear weapons is "not a healthy thing to do ."&

166; It effectively limits your options."

Questions about Clinton's electability were premised on White House adviser Karl Rove's recent comment that no one viewed negatively by more than 40 percent of the country has ever been elected president.

Again Edwards offered praise before snapping the trap, saying Clinton "has done a terrific job" as senator and first lady but refuses to join him in rejecting money from Washington lobbyists. She replied that Edwards was making an "artificial distinction" &

refusing lobbyists' money but taking it "from the people who employ and hire lobbyists." She and Dodd called for public financing of elections.

Obama borrowed from Clinton's own line at another debate &

"I'm your girl" &

to make his case against her. "If you're tired of the backbiting and the score keeping and the special-interest-driven politics of Washington, if you want somebody who can bring the country together around a common purpose and rally us around a common destiny, then I'm your guy."

The Iraq war was much discussed, as it has been in past Democratic debates. In particular, New Mexico Gov. Bill Richardson, whose position among the six establishment candidates is closest to the antiwar protest candidates Rep. Dennis Kucinich of Ohio and former Alaska Sen. Mike Gravel, repeatedly challenged the others to defend why the U.S. should keep residual troops in Iraq after a troop pullout""as they all advocate. The others have cited the need to help avert a regional war over Iraq and combat terrorism.

But Edwards gently admonished Stephanopoulos for "trying to create a fight" by his questions when "any Democratic president will end this war ."&

166; The differences between all of us are very small compared to the differences between us and the Republican candidates ."&

166; They're going to keep this war going as long as it can possibly go."