What make a performance too small to be ‘supporting”?

I have been thinking about this a lot lately. Mainly because there is so much talk about how weak the Best Supporting Actress race for the Oscar is.
At first I would tend to agree, I mean in the so called ‘rules’ of supporting work, it should be over ten minutes, under a half hour and definitely be memorable.

We all know the rules do not work this way. In some cases the screen time creeps over the half hour mark and ventures into lead, when that happens it all depends on who is the biggest star in the film as to who goes supporting.
Catherine Zeta Jones was basically a co-lead, but Renee was the bigger star. Same with Jennifer Hudson and Beyonce, Angelina Jolie and Winona Ryder (at time of nomination) and on and on. There are cases where the categories are switched, usually for child actors or new comers.

Take “The Killing Fields” . Haing S. Ngor (pictured) was a non actor in the film, but was by far on the screen for a good majority of the film. Sam Waterston was a star, had less screen time, but got the lead nomination while Ngor got Supporting (and the win)
Perhaps it had as much to do with race as it did with celebrity status, Tom Cruise and Jamie Foxx in “Collateral” anyone.

Sometimes a co-lead will get bumped to supporting for the simple reason that they will have more of a chance of a win there, Jennifer Connelly in “A Beautiful Mind” is a great example, and one that will forever piss me off.

Julianne Moore (pictured with Toni Collette) and Nicole Kidman is an interesting example. Julianne had more screen time in “The Hours” but was pushed to supporting while Nicole was in lead.
Some people think that Nicole was only pushed because she had more chance of winning in the lead category. I say the movie was about Kidman’s character, so she was the subject and therefore lead.
Another example is Rachel Griffiths and Emily Watson in “Hilary and Jackie”. The film was about them both, but Jackie du Pre was the celebrity, so Watson was in lead, and Griffiths in supporting. Personally I feel there is nothing wrong with this strategy.

The other thought on the Nicole Kidman/Julianne Moore and Tom Cruise/Jamie Foxx situation is that both Moore and Foxx were locks for lead nominations, and to be greedy they (or the studio) put them into supporting so they wouldn’t cancel each other out, and had a better shot at a win (Foxx won, Moore did not). This also pisses me off no end.

This I understand. I get the logic (sort of, if you can call greed and status logic). What I, however, do not get is when people say your performance is too small to be nominated.
If you support the lead actors and you bring something to the film why does the fact you only had 7 minutes make you not eligible?

Vanessa Redgrave, Ruby Dee and Samantha Morton were or are in the race, but people are saying their roles are too small. There are no small roles if you can do something with them.

Take Morton who was given , like, 4 lines of dialogue in “Elizabeth: The Golden Age” get what she does with that time is phenomenal. She creates a fully three dimensional character in a single scene. Not only that, but she makes you feel sympathy for one of the films villains. She certainly did more with her time on screen that Julia did in “Charlie Wilson’s War” and Jules had loads of snappy dialogue to play (fumble) with.

Ruby Dee gives a film bordering on snooze worthy a much need jolt of emotion and spark, and Redgrave ends the film giving it it’s emotional punctuation. Should these actors not be considered for awards consideration because of time?

I just does not seem fair.

I have loads of other films to see yet, and will no doubt face these questions again. I just wish I knew why. Going back a bit, good as Moore was in “The Hours” her part was completely stolen by Toni Collette in a role considered too small to be awards worthy. By what bunch of f*cking twats I would like to know.