A five-minute primer on an issue making headlines Voting takes place today for 427 election committee seats. Who's up for election? The chief executive of Hong Kong. But before he can be chosen, voters have to elect the people who will pick him. Candidates for the Election Committee are drawn from four sectors of the community: industry, commerce and finance; the professions; labour, social services and religious bodies; and public bodies including the Legislative Council and Hong Kong deputies to the National People's Congress. The 800 seats are shared equally between the four sectors and each sector is divided into sub-sectors, each of which has a given number of seats. Think of a pie with 38 slices. There are 38 sub-sectors of the community that get a slice of the vote for the chief executive - and about two-thirds of them match the functional constituencies that elect some legislative councillors. Of the total, 427 seats in 23 sub-sectors are being contested and there are 803 candidates fighting for them. Votes will be cast by about 204,000 registered voters at 110 polling stations from 7.30am to 10.30pm. So what about the other 373 seats? Well, 237 of them are in the 12 other sub-sectors that can elect their members but have no one opposing the nominated candidates. Then there are the 40 members nominated by the six groups in the religious sub-sector, plus all 60 legislative councillors and 36 deputies to the National People's Congress. What's it for? It's called a committee but actually it's the electoral college that picks the chief executive, and some pan-democratic commentators criticise it for being too small. Members sit for a five-year term and a new committee is elected in the six months before every chief executive election. But they haven't had a lot to do since 1997 because the last two chief executives ran unopposed. The members elected today will vote in March. How hot is the contest? The social welfare constituency, where 99 nominees are chasing 40 seats, is one of the hottest. There are four groups battling it out for 20 seats in the higher education sector, and a fierce battle is under way in the accountancy sector, where seven pan-democrats are challenging a 20-member government-friendly list. Why does it matter this time? There's a bit more at stake in the March election because Civic Party legislator Alan Leong Kah-kit is running for the pan-democrats against Donald Tsang Yam-kuen. If Mr Leong can get 100 nominations from the Election Committee, he can stand. But to be sure of getting the nominations, he would need to see 70 to 80 per cent of pan-democratic candidates win today. Will he get these? All bets are off, even among the most seasoned political commentators. Even if Mr Tsang ends up being the only candidate, committee members will still cast their votes in March.