It takes a major social upheaval in the American political system, such as civil war, to cause a major political realignment that goes as far as the downfall of one political party and the rise of another. The Republican Party historically began as an anti-slavery activist party in 1854. (See "Republican Party.") The impetus for the formation of the Republican Party was probably the ineffectual opposition of the Whig Party (which preceded it) in the face of Democrat President Franklin Pierce' support of the Kansas-Nebraska Act, which destroyed the so-called Missouri Compromise.
In short, the activists who formed the Republican Party feared that the United States would evolve into a country where every state in the union sanctioned the ownership of slaves. The Republican Party didn't supersede the Whig Party, however, until 1860, with the election of Abraham Lincoln. The candidacy of Lincoln, and the fortunes of the Republican Party, received a big boost from the Supreme Court's fatal 1857 decision in the Dred Scott v. Sandford case, which involved a slave that had escaped to a free state, and was forced to be returned to his southern owner.
Given the present direction of the Democrat Party, similar outrage might eventually be raised regarding issues like abortion and same-sex marriage, and given the present direction of the Republican Party, such outrage might be raised regarding the various and sundry doctrines of military interventionism. We already see a major upheaval regarding deficit spending.
Such upheavals are inevitable in our system, because every political party works overtime in the effort to build a winning coalition in our morally diverse culture. In effect, to ensure a majority in the next election, a party must make a pact with the Devil. Such a pact always trades long term destruction for short-term success.
Common sense and sound and coherent moral imagination are increasingly rare in our secularist consumer culture. It's very hard for common sense and sound moral judgment to hold decisive sway in either political party, because the numbers of the wise are insufficient. At present, the Republican Party is generally sympathetic to giving at least lip service to things like "respect life," "respect marriage," "respect conscience," "respect property," "respect the right to self-defense," "respect the Constitution" and "respect the sovereignty of other nations." It's far too much to expect such a large Party apparatus to understand, much less appreciate, the vital need for the principle of subsidiarity. Nevertheless, it is frequently acceptable for a moral purist to support the Republican standard bearer in opposition to the Democrat, and that is sufficient to guarantee the survival of the party.
Furthermore, the Electoral College election system ensures that one of the two major parties is virtually assured of winning a majority of the electors, and thus the Presidency, every four years, even in times when third party challengers rob both of the major parties of a majority victory. This is a consequence of the decision of most states to assign "winner-take-all" status to the plurality:
Voters in each state and the District of Columbia cast ballots selecting electors pledged to presidential and vice presidential candidates. In nearly all states, electors are awarded on a winner-take-all basis to the candidate who wins the most votes in that state. Although electors are not required by federal law to honor a pledge, in the overwhelming majority of cases they vote for the candidate to whom they are pledged.
As a consequence, Duverger's law applies. (See "Factors in a Two-Party and Multiparty System.") In social systems theory terms, there are always homeostatic survival forces at play to crush any possible challenge by a third party, such as the Libertarian Party or the Green Party, as well as all efforts at internal reform. (See "Systems psychology" for a discussion of the role of homeostasis.)
This is complicated by the process of moral drift, which quasi-static systems, such as our two major parties, are always subject to in the search for an effective majority coalition. In a two-party system, the logic of "big tent theory" trumps moral coherence and integrity, and all of the major players are inevitably corrupted by it.
Furthermore, those with the skills and connections to put together such coalitions tend to drive the parties, regardless of their moral or political background. At a practical level, this has resulted in the dominance of neo-conservatives in the Republican Party (which used to be dominated by the so-called Rockefeller wing) and the dominance of Malthusian socialists in the Democrat Party, and both parties are dominated by supersidiarist thinking and foreign adventurism. The reason is quite simple, really, both supersidiarism and foreign adventurism are the natural products of elite hubris, and elites have a built-in advantage in the coalition-building game.
These parties were not always thus. In 1952, the Republican Party chose General Dwight D. Eisenhower, the hero commander of the European Theater of Operations in World War II, as its standard bearer. Eisenhower was no interventionist. On the contrary, he opposed intervention in the Suez Canal incident, and America stood by as the Russians erected the Soviet Union, largely during Eisenhower's tenure. It turned out, of course, that control of the Suez Canal was not as vital to trade as our European partners imagined, and the rise of the Soviet Union actually accelerated the eventual collapse of Russia's world power.
Similarly, President Kennedy went against the grain of the Democrat Party when he called for a major tax cut to stimulate the economy, and America stood largely aloof to the penetration of Communist ideology in Southeast Asia until Kennedy was assassinated. Kennedy, lacking the character and the burnished aura of an Eisenhower, might very well have succumbed to the siren song of interventionism had he lived, though he might eventually have grasped the futility of propping up a corrupt anti-communist regime in Viet Nam. The possible role of the U.S. in the coup that replaced President Diem at the beginning of November in 1963, however, suggests that Kennedy was still going to school in the field of foreign relations before he, himself, was assassinated at the end of that very month.
President Reagan went against the elites when he refused to give open-ended support to the military mission in Lebanon. President Clinton went against the elites when he went along with welfare reform. Reagan also went against the elites when he enacted the Mexico City Policy in 1984. The rarity of these examples indicates the difficulty of challenging the general drift of elitism in foreign and domestic policy.
It remains to be seen whether a President Romney, should he be elected this November, will be able to put together a coalition to roll back even federal base-line budgeting, much less the long march of federal intrusiveness in every aspect of our lives. Its likely that the only thing that can effectively challenge elite hubris is the total collapse of the American economy or the total breakdown of social order, or both.
Meanwhile, all efforts to reform the two-party system will most likely be crushed through demonization of the challengers. We have already seen this in the demonization of the so-called Tea Party movement, a demonization that is operative in both major parties, as well as the demonization of so-called family values groups within the Republican Party. From a systems theory perspective, this is all very predictable.
And this drift in the context of irreformability would be operative within these two parties regardless of whether the electoral system was majority-rule or plurality-rule. The principle impact of plurality-rule, as we have it today, is to ensure that third party challenges are nominally counter-productive.
It is easier for a camel to pass through the eye of a needle than for a major party to reform at the level of fundamental principles.