WASHINGTON — John Edwards has been taking rhetorical shots at Senator Clinton almost from the start of the presidential campaign, but three months before the first votes are cast, he is not quite ready to answer the chief question surrounding her candidacy: Can she win?

The former North Carolina senator has adopted an increasingly aggressive stance in confronting the Democratic front-runner on the war in Iraq and the influence of Washington lobbyists, saying she would not represent enough of a change from the Bush administration.

Yet when it comes to the most biting criticisms of the Clinton legacy, or the argument that Mrs. Clinton is unelectable and would hurt Democratic chances in 2008, Mr. Edwards begins to hem and haw. For now, it seems he is content to let others — namely his wife and key advisers — throw the verbal punches.

That tack was particularly evident yesterday.

In an appearance on NBC’s “Meet the Press,” Mr. Edwards criticized Mrs. Clinton’s Iraq stance even as he refused to echo statements by one of his strategists, David “Mudcat” Saunders, that “the Clintons screwed” rural America in the 1990s and that the former first lady would carry “toxic coattails” atop the Democratic ticket next year. He also tiptoed around a statement by his wife, Elizabeth, that the “hatred” of Mrs. Clinton would “energize the Republican base” in 2008.

The exchange has become something of a pattern for Mr. Edwards, in which Mrs. Edwards or one of his aides will treat his chief rival more harshly than he does.

Ordinarily, his decision to hold back would be seen as a strategy aimed at keeping him in the running for the vice presidential slot if Mrs. Clinton wins the nomination. But such a theory is lessened by the fact that he has already run on a losing Democratic campaign with Senator Kerry in 2004 — and more specifically by his failure to win even his home state of North Carolina for Mr. Kerry. “I think it’s extremely unlikely he would be on the ticket,” the director of the University of Virginia’s Center for Politics, Larry Sabato, said.

On NBC, Mr. Edwards was asked about Mr. Saunders’s comments to the Boston Globe last week, in which he referred to a swing through northern New Hampshire that the candidate was taking as the “Let’s help John Edwards screw those who screwed us tour” — with “us” meaning rural America.

“Who screwed us?” Mr. Saunders was quoted as saying. “The Clintons screwed us. Anyone that says different is delusional.” As examples, he cited President Clinton’s support of the North American Free Trade Agreement and Mrs. Clinton’s ties to Wal-Mart. Mr. Edwards responded yesterday with a chuckle. “Well, Mudcat has a way of saying things that I wouldn’t say exactly the way he does,” he said, before deferring to the more veiled critique of Mrs. Clinton that he employs on the campaign trail. “I believe we cannot replace a group of corporate Republicans with a group of corporate Democrats,” he said, referring to Mrs. Clinton’s refusal to denounce lobbyists and the special interest culture in Washington.

The reaction was similar when Mr. Edwards was asked about Mr. Saunders’s remark on MSNBC last week that Mrs. Clinton’s “toxic coattails” would cost the Democratic Party seats in the House and Senate, along with the White House. That sentiment was also voiced by Mrs. Edwards, who told Time magazine that while she doesn’t think the “hatred” of Mrs. Clinton in some quarters is justified, “you can’t pretend it doesn’t exist” and that “it will energize the Republican base.”

The Edwards campaign has long pushed the argument that he is the most “electable” Democrat, but it has rarely used such stark language in support of the notion that Mrs. Clinton is too divisive and polarizing to win a general election. “I honestly don’t know the answer to that,” Mr. Edwards said when asked if Mrs. Clinton would drag down the Democratic ticket. “I mean, I think there’s a lot of conflict out there about that question.”

He expressed a general sense of agreement with his wife, but he stressed his own credentials as a candidate who had won election to the Senate in a “red state,” North Carolina.

“What I know that is that voters have a very clear choice — Democratic voters have a very clear choice between Senator Clinton, both with all of the good and bad that comes with her, and John Edwards, who has actually won in a red state and who could compete in every single place in America,” he said.

As if to emphasize his hesitation, he added: “I’m not saying anything bad about Senator Clinton. She’s a good candidate.”

Mrs. Edwards has often been willing to go further than her husband in criticizing Mrs. Clinton, most notably on her record on women’s issues and health care. That is no coincidence, Mr. Sabato said. “That part of the equation is definitely calculation,” he said.

While saying Mrs. Edwards was “outspoken,” a senior campaign adviser, Joseph Trippi, denied that her candor was strategic. “No one on the staff tells her what to say,” he said yesterday. “This is the most non-calculating family I’ve ever worked with.”