European political parties are made up of people who share the same ideological view. If there are 27 parties in the French National Assembly, that's because 27 major political ideologies prevail in the country.
American, and British, political parties are coalitions of major ideological tendencies. The strongest ideology in the Republican party is fiscal and social conservatism tempered by a large number of so-called moderates.
The Democratic party is to the left of the Republican party. In William Jennings Bryan's 1896 "Cross of Gold" speech, he defined the Democrats as the party of the people - of farmers, workers, and the rootless poor; the Republicans, said Bryan, were the party of the wealthy and entrepreneurial classes.
Bryan accurately described the differences between the two major parties. But their similarity as two coalitions is fundamental to their continuous existence. That's why the two conventions have echoed the theme of unity - although both parties were fractured, if not shattered, this summer.
The Republican convention at San Diego was split over the abortion plank in its platform; the party's right wing was in the ascendancy. A majority of this week's Chicago convention delegates were old-fashioned Democrats - which is to say liberals. But the platform and the staging of the convention itself were in the hands of New Democrats. President Clinton's decision to sign the Welfare Reform bill became the issue which divided the old liberals and the New Democrats - who are personified by Mr. Clinton himself.
If the Republicans lose both the White House and the House this year, they will be back in the minority - which has been their status for many years.
But if the Democrats lose the White House in November, their differences over social policy would be exacerbated. Such issues are the foundation of the modern Democratic coalition. And the future of the oldest political party could be in danger of schism.
*Rod Macleish is Monitor Radio's Washington editor.