Some of the immutable laws of politics:
If it walks like a duck and it quacks like a duck, it's a duck.
If on the other hand it can't make a noise and waddles and then falls over, it's a lame duck.
And a president at the end of a second term with a highly partisan Congress ranged against him is as lame a duck as you will ever see.
So maybe it's time to rewrite those immutable rules. Because on Thursday the president looks anything but lame. The signature legislative achievement of the Obama years was to drive through the Affordable Care Act - or Obamacare as it is more widely known - that has given health insurance to millions more Americans.
It had been a Democratic ambition for 50 years to overhaul healthcare in the US. People in Washington and around the country have been waiting on a ruling from the Supreme Court on quite a narrow challenge to Obamacare, but which if it had been successful would have caused total chaos in its implementation in about 30 US states.
The stakes could not have been higher. People's health (crucially important) and Obama's legacy (less important, but for him and those around him fairly vital) were at stake. Well a politically finely balanced Supreme Court has given an emphatic, overwhelming vote in favour of the President by 6-3.
I bet no-drama Obama is high fiving anyone and everyone in the White House - that is how big it is.
Add to that the TPP trade deal with Asia. That is huge too. Congress (yes, do you remember back in November after the midterms when everyone was predicting that nothing would ever get done again, and how it would be total gridlock until after the elections in 2016?) last night gave Barack Obama 'fast-track' authority to complete what the Financial Times describes as "the most ambitious regional trade deal in recent history".
With Japan and the US and 10 other countries involved the deal accounts for 40% of world trade. And it should be said, this was won in the teeth of opposition from many Democrats, and the labour unions in the US. Obama now wants to repeat that victory with a similar deal with the Europeans. There is still a long way to go after all there's many a slip twixt cup and lip (ask Dustin Johnson after his three putt from 12ft that cost him the US Open last weekend.)
But last November no one would have thought we would have been here. Another bit of the legacy in place.
And then there is Cuba, where the US and the Caribbean island seem on the cusp of resuming diplomatic relations after a recent history that brought the world the closest to nuclear war in many of our lifetimes. And on the subject of which, it maybe that the P5+1, led by the USA, is on the edge of concluding a deal with Iran that - if you buy the Obama administration narrative - will prevent Tehran from realising its nuclear ambitions.
Wherever you stand on the rights and wrongs of the Iran deal - and there are strong passions and deep concerns aroused by this - it is hard to present a storyline of an administration becalmed, sails flapping, bobbing up and down, going nowhere. Whether it is going in the wrong direction is a different question
And if someone from the White House press office were looking over my shoulder they'd be no doubt chipping in saying: "And what about the jobs creation, and the turnaround of the US economy since the financial crisis..."
But today is today and tomorrow is tomorrow. As I write this Obama is about to come into the Rose Garden to salute his famous victory on Obamacare. Tomorrow, though, he will board Air Force One with the First Lady, the Vice President and his wife to travel the 400 miles south to Charleston to deliver the eulogy at the funeral of his friend. Clementa Pinckney was one of the nine shot dead by a white supremacist in the most cowardly act imaginable - gunned down in their church as they gathered for a bible study class. Obama's legacy there is more uncertain.
America is very much not living in post-racial harmony. The events of the past year have been ugly, with race riots, a high number of black men killed by white police officers for no apparent reason, and now the horror of Charleston. And there is gun crime. After the Charleston shootings there was a note of resignation and failure in the president's voice as he bemoaned America's record to tackle this issue. Race and guns will go very much into the 'tried and failed' folder.
Churchill is widely quoted as saying that history is written by the winners. What he actually said was that he was confident history would find the then prime-minister Stanley Baldwin wrong - and with a big grin on his face added "because I shall write that history". He then knocked out at great speed his six-volume History of the Second World War, published between 1948 and 1954, which came to dominate Western thinking about the conflict for a generation.
It is too soon to write anything decisive about Obama's legacy. But if the Supreme Court had ruled against him on Thursday, and if the trade deal had faltered - then there would be many writing his political obituary.