Washington ? The party-line vote in the Senate Judiciary Committee to confirm Judge Samuel Alito for the Supreme Court, presaging a similar outcome in the full Senate, certifies the depth of the division between Republicans and Democrats on basic national policy.

That reality shadows the start of this session of Congress and raises doubt about the government’s ability to address any of the major challenges facing the country.

The layoffs announced this week at Ford, coming after those decreed earlier at General Motors and Delphi, spell out the threat to America’s industrial base. Runaway health care costs for the automakers’ retirees are a big part of the problem, but a Congress wracked by partisanship has been stuck in neutral on systemic health reform for over a decade.

The same thing is true when it comes to Social Security, to energy and to the management of the federal budget. Party-line votes in all these areas have become the basic pattern. Of 28 votes in the House and Senate last year, identified by Congressional Quarterly as the key roll calls for the session, majorities of the two parties opposed each other on all but five.

In the House, the subjects that provoked disagreements included immigration rules, stem-cell research, surveillance and interrogation policies, arms sales to China, the Central American Free Trade Agreement (CAFTA), the Endangered Species Act, energy, and the intervention in the Terri Schiavo case.

In the Senate, the parties split on class-action lawsuits, bankruptcy protection, CAFTA, the Patriot Act, the budget, defense appropriations, energy, and the nomination of John Bolton to the United Nations.

The variety of subjects indicates the broad dimensions of the party differences. They embrace social, cultural, economic and foreign policy issues. The only notable area of agreement between the parties was on the big transportation bill, loaded with pork-barrel projects for both Republicans and Democrats.

Overall, Congressional Quarterly reported that 2005 was one of the most partisan years since it began its record-keeping. It found that the parties took opposing stands on 328 of 669 roll calls in the House and 229 of 366 in the Senate. In the 11 years since the Republicans took over the House, the percentage of party splits has been higher five times. In the Senate, only twice has it exceeded that level.

Even more striking is the cohesion within each party. On the roll calls where the parties divided, nearly nine out of 10 Republicans and Democrats voted the party line. The average House Republican was loyal 90 percent of the time; the average for House Democrats and for both parties in the Senate was 88 percent.

Republicans have been about that united since taking over. The Democratic discipline has been trending upward, especially in the House, where it averaged 81 percent in the first four years of minority status, compared to 87 percent in the latest four years.

What once was a clear regional split among Democrats, with the Dixie contingent voting often in a conservative bloc with Republicans, has diminished if not disappeared. Last year, Southern Democrats in the House were only 9 points lower in their loyalty to the party position than Northern Democrats; in the Senate, the difference was 8 points.

In all of Congress, only two people voted more often with the opposing party than with their own on the party-splitting roll calls. Sen. Lincoln Chafee, the Rhode Island Republican, and Sen. Ben Nelson, the Nebraska Democrat, opposed their party’s majority about 53 percent of the time. Of course, President Bush won Nebraska and John Kerry ran away with Rhode Island, so these senators – both facing election this year – had reason to trim their sails.

In an excellent article in the Jan. 21 issue of National Journal, Carl Cannon summarizes the political science community’s explanations for the many reasons underlying this intense partisanship. They range from the way families are choosing their neighborhoods and communities to the way district lines are drawn, from the massing of campaign funds to the tone of cable TV talk shows and the way George Bush has conducted his presidency.

But the inevitable conclusion is that the pattern we have seen is likely to continue – at least until the American public really rebels against this extreme partisanship and finds a way to demand a different approach to governing.