If you are confused about this talk of Republican John McCain joining Democrat John Kerry’s ticket, here’s an explanation.

Kerry probably doesn’t really think McCain will abandon the GOP despite his barely concealed disdain for President Bush. Besides, as admirable as the Arizona senator is as a person and public official, he lacks the personality and temperament to be No. 2.

But floating his name and those of other Republicans like Sen. Chuck Hagel of Nebraska signals that the Democratic candidate understands that, if he hopes to govern effectively, he will need to overcome the bitter partisanship that has paralyzed Washington in recent years.

It also provides a contrast with Bush, who, despite campaign vows to be a uniter, rarely has reached out to his foes.

The Kerry gambit comes at a time of rising concern among both nonpartisan analysts and political partisans over the corrosive impact of infighting on everything from policy decisions to which party is most responsible.

Interestingly, each of the last three presidents entered office with an inaugural address vow to end the wrangling. But it hasn’t happened, and the situation has gotten worse. There’s plenty of blame to go around.

In the 1980s, House Democrats used their majorities to seat the Democrat in a disputed Indiana election and to limit Republican floor amendments. Now that Republicans control the House, they use their majority to curb debate and often don’t consult Democrats on legislative business.

When Democrats held the White House, the Senate’s Republican majority blocked judicial nominations. Now, Democrats use the rules that protect minorities to block GOP choices.

And the degree to which the once bipartisan Senate has come to resemble the highly partisan House was illustrated last weekend when Senate Republican leader Bill Frist went to South Dakota to campaign against his Democratic counterpart, Tom Daschle.

Much of the problem has played out from opposite ends of Pennsylvania Avenue.

When Bill Clinton won the White House in 1992, Senate GOP leader Bob Dole promptly announced he would stand up to him in behalf of the 57 percent who voted against the winner. Later, congressional Republicans tried to oust Clinton from office.

When Bush won the disputed 2000 election, Democrats vowed to fight him at every turn. Democrats who cooperated with him found him campaigning against their re-election.

The obvious question is: When and how can it end? The bitterness evident in the comments and commercials by the principals in this year’s election underscores the need for someone to take the first step.

But that won’t be easy, regardless of the November outcome.

If Bush wins, he will have to go a long way to overcome the hostility engendered by his scorn for lawmakers of both parties and his refusal to consult with them. The likelihood he would have bigger House and Senate margins in a second term might make accommodation even less likely.

If Kerry wins, he will have to build bridges to the GOP to have any success, given the fact that he almost certainly will have a Republican House and possibly a Republican Senate. His efforts to reach out to GOP senators suggest he understands that.

Even if Kerry doesn’t pick a Republican running mate, he might follow the example of past presidents who gave key posts to the opposite party to illustrate the goal of seeking middle ground. But a lot may depend on how the defeated party reacts to the outcome. A decisive result might prove more persuasive than another cliffhanger.

A generation ago, congressional Democratic leaders like Sam Rayburn and Lyndon Johnson worked closely with Republican President Dwight Eisenhower, and Republicans like Everett Dirksen helped Johnson pass the landmark 1964 Civil Rights Act.

Now, until something changes, the polarization of the parties is reflected in their leadership, making confrontation, rather than cooperation, the norm.

Carl P. Leubsdorf is Washington bureau chief of the Dallas Morning News