Like a satellite launched into orbit, destined from the outset to be reclaimed by gravity, all presidencies reach their zenith and begin to gradually decline.
Tracking the precise point at which a president begins to fall back to earth in his second term is part political science, part intuition, and every bit a favorite Washington pastime.
And now the whispers have started in the aftermath of President Clinton's failure to win congressional approval for "fast track" trade negotiating authority. Is he losing power? Has he become a lame duck?
Perhaps, say a few analysts of the office. But others say it's far too soon to make that call - and that fast track was a complicated, atypical issue.
What the vote really revealed was that there are few "Clintonite" lawmakers who will follow the president's lead, say analysts. Furthermore, Mr. Clinton's penchant for centrist issues, such as free trade and welfare reform, has alienated many liberals in his own party.
"[Clinton] hasn't built up a base for the Democratic Party, and he hasn't built up a grass-roots following in the country," says Allan Lichtman, a political historian at American University here.
Issue by issue
That leaves Clinton in a peculiar position a year before midterm elections. He has factions of support and opposition, sometimes in equal measure, within both parties, depending on the issue.
As a result, if he is to remain viable on the legislative front, Clinton will be more dependent than ever on the use of issue-driven coalitions rather than traditional party alliances.
"Politics have become more issue-specific," says Democratic pollster Mark Mellman. "He [Clinton] is going to find himself with Democrats on some issues and with Republicans on" others.
"It means he has to work more," says Thomas Mann of the Brookings Institution, a Washington think tank. "He'll have to create majority coalitions himself."
That reality dims prospects for final epic battles the administration faces in reforming Medicare and Social Security.
It also makes Clinton unique among recent presidents. Most had a core group of acolytes who voted with the White House, no matter what.
Take Ronald Reagan. Despite the crisis of the Iran-contra scandal, Mr. Reagan remained vital in his second term because of his strong ideological base.
While the lame-duck label may be premature, most analysts agree Clinton is already being more aggressively challenged from the left and right.
Indeed, the fast-track issue wasn't Clinton's only setback in Congress last week. The House and Senate joined forces to override his line-item veto of a military construction measure. And Senate Judiciary Committee chairman Orrin Hatch (R) of Utah nixed the nomination of Bill Lann Lee, Clinton's choice for assistant attorney general for civil rights.
"Congress has been sticking it down his throat on appointments, and that's the sign of a president who doesn't have a lot of clout," Mr. Lichtman says.
It's been tough all along
Even the administration admits concern over the flurry of lame-duck speculation. But it claims that the political environment has actually changed little for Clinton.
The speculation, some point out, does not take into account the fact that Clinton has had a tough time in Congress throughout his presidency. He has suffered tough losses, including health care. Where he has won, as in the case of his first balanced budget, it was by the slimmest of margins.
When lawmakers have followed the president, they did so not out of fear of a Lyndon Johnson-brand of retaliation. Rather, success has been realized when choices were framed in ways that make support politically feasible.
Others point out that Clinton is an adept political figure who may not dominate politics or the national agenda but who is still in a position to move the public policy debate.
"The real negative I can see after [the fast-track loss] is it hampers his ability to pursue a moderate course," observes Georgetown University Prof. Stephen Wayne.