Choosing his running mate is the biggest decision John Kerry will make in his presidential campaign. And by this time next week, we will probably know what the decision is.
John Kerry will announce his running mate soon
It matters because the announcement will receive saturation coverage in the media.
People who have not given politics much thought up to now will take notice.
The choice will tell us a lot about Mr Kerry: whether he is a risk-taker, what he values, and how he wants to position his candidacy.
Among the Democratic grassroots, the clear favourite is Senator John Edwards.
When you talk to Democratic activists, they repeatedly describe Mr Edwards as "exciting" and "fresh", suggesting these are qualities which they think is missing in Mr Kerry himself.
There are other advantages to choosing Mr Edwards: his southern, more socially conservative politics would help to offset Mr Kerry's north-eastern liberal image.
His emphasis on domestic issues would balance Mr Kerry's obvious foreign policy strengths. His boyish charisma would add some zip to Mr Kerry's ponderous stump style.
He is also the favourite with the ordinary voter.
A recent Gallup poll showed that 72% of respondents want Mr Edwards compared to 64% for the former Democratic leader of the House, Dick Gephardt - though that may just be because his is the most well known name in the frame.
Despite this, Mr Edwards could still be ruled out.
Some Democrats say Mr Kerry just doesn't like Mr Edwards. But he wouldn't be the first candidate not to get on with a running mate. Eisenhower, for instance, despised Richard Nixon.
A more serious claim is that Mr Edwards, a first-term senator, could look vulnerable on foreign policy when going toe-to-toe against Vice President Dick Cheney.
The Kerry camp may decide Mr Edwards won't deliver any of the key swing states. Or they might find something in his past which would embarrass the ticket.
But if he doesn't pick Mr Edwards, the Kerry camp will have to brace itself for an angry backlash among the grassroots.
A lot of Democrats are afraid that Mr Kerry will end up choosing Mr Gephardt.
Politically, it's hard to see why Mr Kerry would choose him, except that he could deliver Missouri, his home state.
Mr Gephardt is much closer to Mr Kerry in both substance and style. Mr Kerry clearly feels more at ease with Mr Gephardt's rather stolid legislator manner than Mr Edwards' populism.
But choosing Mr Gephardt could cause a lot of the air and excitement to evaporate from the Kerry campaign.
Wild card candidates
The John McCain rumours have stopped. The Republicans have signed him up as a keynote speaker at their convention.
I suspect that the Kerry camp was never actually serious about Mr McCain, but was happy to fan the rumours because it made Mr Kerry look more appealing to the centre ground.
In the same vein, William Cohen is now being mentioned.
Mr Cohen is another Republican, but unlike Mr McCain, he has served in a Democrat administration, as President Clinton's defence secretary.
Mr Kerry could pick another Vietnam veteran, Wesley Clark
Another wild card is Bob Rubin, Mr Clinton's treasury secretary. These are both riskier choices because they wouldn't deliver any political constituency.
But President Bush's problems in Iraq may make Mr Kerry feel more confident about taking a risk.
And if he is, he could go for a fellow Vietnam veteran, Wesley Clark. He has the charisma of Mr Edwards, but lacks the political base to threaten Mr Kerry.
Iowa Governor Tom Vilsack and Indiana Senator Evan Bayh are possible compromise candidates.
They are unknown outside Democrat circles. But they are popular, competent moderates - John Edwards without the star wattage - and no one would complain that much if one of them received the nod.
Choosing a running mate is a gruelling process.
A candidate has to be willing to subject himself (there are no women in the frame unless you include Hillary Clinton, who is 100/1 long shot) to intensive interviews in which everything - his sex life, his finances, his friends - is discussed.
Teams of lawyers pore over every available public record from credit records to high school year books. Past girlfriends are contacted.
John Kerry went through the process last time as one of the favourites for becoming Al Gore's running mate. The other unsuccessful candidate on the short list was - John Edwards.
Closely guarded secret
Less than 10 people really know who it is going to be. Mr Kerry has consulted his wife, his brother, his chief of staff, his chief strategist and of course, Jim Johnson, the man heading the search committee, but he has successfully kept the process away from the cameras, thereby heightening the sense of anticipation.
Running mates can certainly boost a candidate. But they can also doom them.
Dick Cheney, the acclaimed choice of George Bush in 2000, is now seen as an increasing liability by moderate Republicans.
Not because of anything he has done, but because of this image of secretiveness and corporate connections which surrounds him.
A candidate has to be very careful of the company he chooses.