The US Senate has begun debating the nomination of a controversial senior judge which could trigger a chain of events leading to a showdown over the practice of filibustering - or blocking legislation by debating it at length.
The tradition of the filibuster is almost as old as the Senate itself
Republicans have threatened to change Senate rules in order to stop Democrats from filibustering nominations with which they disagree.
On the face of it, the looming Senate battle over the filibuster is an esoteric row about a quaint but inconsequential parliamentary practice.
Yet at the heart of this debate is a very consequential issue: power.
Unless a last minute deal is reached, the Democrats have said they will filibuster several of President George W Bush's nominees to senior judicial positions because of what they argue are their extremist views on issues such as abortion and gay rights.
Senate Minority Leader Harry Reid, a Nevada Democrat, said: "The filibuster is a critical tool to keep the majority in check."
He accuses Republicans of "an arrogance of power" in threatening to abolish it.
"They think they are wiser than our Founding Fathers. I doubt that's true," Mr Reid said.
'Drift to right'
Although the Republicans control the presidency and both houses of Congress, the ability of Democrats to block these nominations is a serious challenge to their agenda, both now and perhaps more importantly, in the future.
For this tussle over these nominations is in many ways a dress rehearsal for an even bigger row over vacancies in the Supreme Court, which are expected to occur in the next few years.
Grover Norquist is President of Americans for Tax Reform and a leading right-wing thinker, who has the ear of Mr Bush.
"Eventually as more liberal judges or activist judges retire or pass away and are replaced by judges confirmed by a Republican Senate, the courts - the Supreme Court in particular, but the courts in general - will drift to the right," he told the BBC.
In a country which holds its system of checks and balances in such high regard, the Republican leadership threat to change the Senate rules in order to block judicial filibusters has been divisive.
There have been plenty of words spoken already.
Both sides have been filling the airwaves with adverts - defending or attacking the prospective federal judges who are under the spotlight.
And, as the first nomination, that of Priscilla Owen, was presented in the Senate, Majority leader Bill Frist called for less talking and more voting.
"Debate the nominee for five hours. Debate the nominee for 50 hours. Confirm the nominee. Reject the nominee. But in the end, vote," he said.
The filibuster is a way of giving the minority party some measure of influence and some Republicans with longer memories are concerned about the precedent that removing it would set.
Supporters of what's become known as the "nuclear option" because of its destructive potential argue that the Democrats' actions go beyond the Senate's remit to advise and consent.
In the next few days, it should become clear whether they are prepared to push the nuclear button.