The presidential race continues to be on the knife’s edge. In 15 polls taken since the third debate on October 13, President Bush has had an average lead of 49% to 46% over Senator Kerry. Mr. Bush’s percentages of support ranged between 46% percent and 52%, Mr. Kerry’s between 42% and 49%. In Florida, Ohio, and New Hampshire – states Mr. Bush carried in 2000 – and in Wisconsin, Iowa, and New Mexico – states Vice President Gore carried in 2000 – different polls show both candidates ahead.

It was no accident that last week the presidential and vice presidential candidates made 53 of their 59 campaign stops in these states, plus similarly close Pennsylvania and Minnesota. The overall picture is a little more favorable to Mr. Bush than to Kerry. But any Bush margin that exists now could disappear by Election Day.

We have had close elections before, but not usually ones attended by such bitterness and anger. The 1968 race between Richard Nixon and Hubert Humphrey, and the 1976 race between Gerald Ford and Jimmy Carter turned out to be very close, closer indeed than expected. But few partisans on the losing side considered the winner unacceptable. That’s not the case today.

In the debates, Mr. Kerry recalled that Bush campaigned in 2000 as a unifier, not a divider, and criticized him for dividing the nation as president. Yet the harshest rhetoric of this long, long campaign season has come, not from Mr. Bush and the Republicans, but from Mr. Kerry and the Democrats. Democrats have called Mr. Bush and Vice President Cheney unpatriotic, not the other way around; Democrats have charged that Mr. Bush was “AWOL” in the Texas Air National Guard; Democrats have claimed that Mr. Bush “lied” about Iraq. The Democrats are the opposition party, and as such can be expected to attack the incumbent. But they are not conducting a campaign that will make it easy for them to unify the country if they win.

Nor have they been conducting themselves in a way that will make it easy for them to govern. One of the hardest things in politics is to come up with campaign proposals that will help you win the primaries, help you win the general election and help you govern. Bill Clinton did a good job of this in 1992, though he made a detour on health care in 1993-94. Mr. Bush also did a good job of this in 2000, although the September 11 attacks led him to refashion foreign policy as no other president has done since Harry Truman in the Cold War.

Mr. Kerry has not done such a good job. Never much absorbed in policy issues in the Senate, he has had a weak policy shop. His major domestic initiative, on health care, has features that helped in the Democratic primaries but will be problematic if he is elected. Mr. Bush has innovative positions on Social Security and health savings accounts, but it’s not clear that he’s given them enough emphasis to get them enacted.

But those are not the things that are likely to drive voters’ decisions. This is an election about foreign policy and basic values. It would be easier for the winner to govern if he could win an unambiguous and uncontested majority. Can that happen?

There are two theories about how voters could break toward one candidate or the other candidate. One, held by Democrats, is that most voters have rejected Mr. Bush and are just waiting to make sure Mr. Kerry is an acceptable alternative, as voters decided to go with Ronald Reagan over Mr. Carter in 1980. But Mr. Bush’s job rating is higher than Mr. Carter’s.

Another theory, held by some Democrats as well as Republicans, is that voters will decide not to switch presidents in time of war and will surge toward Mr. Bush. Possibly spurring such a reaction is the increasingly vitriolic tone of the Kerry campaign and the 527 organization ads against Mr. Bush.

The Kerry campaign deliberately tried to avoid that tone at its convention and sounded it again only in September, after Bush built up a post-convention lead. But there can be a backlash to vitriol, as Minnesota Democrats discovered after the bile unleashed at Paul Wellstone’s funeral in 2002. Democrats, living in a cocoon where Bush hatred is universal and unexceptionable, failed to anticipate that. Have they made the same mistake again?