This question, which I seem to recall hearing way back in grade school, is fundamentally silly. In nature, there are no absolutes. So the simply answer is: we discover that the force was not irresistible, or that the object was not immovable, or both.
The "Immovable" Object:
Surely, one of the most remarkable and enviable traditions of American politics has been that of the peaceful transfer of power. Never in our history has a President and his administration been removed from office by force of arms. Instead, it has been our tradition that when, following an orderly election, a new President is inaugurated, he is usually greeted by his predecessor at the White House, whereupon they ride together to the inauguration ceremony. Then the former President begins an honorable retirement, writes his memoirs, and accepts six-figure speaking engagements.
No longer. For perhaps the first time in our history, a significant number of administration officials and supporters, including perhaps the President himself, must keep themselves and their party in power to avoid criminal indictment, conviction, and imprisonment. For it can scarcely be doubted that these individuals have committed numerous crimes, as they have, in fact, proclaimed themselves above the law. Among these crimes: disclosure of a covert intelligence agent, waging an illegal war, lying to Congress, violation of the Geneva accords on treatment of prisoners, unlawful incarceration of both citizens and aliens, illegal surveillance of private citizens, bribery, and much more. These crimes are well known. Surely there are many additional crimes that have been successfully hidden by this secretive regime, but would likely be discovered and prosecuted should an opposition party take control of the government.
Thus the Busheviks simply can not afford to relinquish power. Not the White House in 2008, and not either house of Congress in November, for that would allow the opposition party to conduct Congressional investigations of the behavior of the Bush regime.
This the GOP will not allow, and they are in a position to prevent it, whatever the cost and whatever the methods required, including election fraud, regardless of the wishes and the actual votes of the American people. There is abundant and compelling evidence that they have committed election fraud in the previous three national elections, notwithstanding the dogged refusal of the mainstream media to report this evidence or of the Democratic party to recognize the fraud and to initiate criminal and civil action against these crimes.
Absent any dramatic breakthroughs in the investigation of election fraud, and absent the widespread adoption of reliable methods of voting certification, it is virtually certain that the Republicans will once again steal the Congressional elections in November, and the Presidential election of 2008. And Lincoln's government of, by and for the people will be no more.
Yet the Democrats and the media pretend that these pending elections will be fair and accurate, just like all the others, and that the Democrats have an excellent chance of regaining the Congress in November, and the White House in 2008. Talk of stolen elections, past and future, is just not acceptable in polite political conversation.
Accordingly, a perpetual GOP control of government appears to be an immovable political object.
The "Irresistible" Force:
The good news, is that these conditions are not likely to remain in place. For even now, some significant events are afoot. Among them:
Bush and Cheney have taken on the New York Times, which has heretofore been a Bush enabler. And this time, several "conservative" newspapers have come to the defense of the Times, and more generally, the First Amendment freedom of the press. Will more of the print media follow in support? To the Busheviks, it is not enough that the media be supporters; the media obedience must be total. Now the high-voltage Bushevik charges of "treason" over the New York Times' disclosure of the latest Bushevik outrage may pull the it back into line, or it might be the final straw that chases the Times off the reservation. If so, where the Times leads others may follow.