The southern John Edwards could balance John Kerry's ticket
Picking a presidential running mate is a cloistered affair.
Perhaps not quite so full of arcane ritual as picking a pope - but certainly just as secretive.
As Michael Dukakis's press secretary once said: "Anybody who knows anything will tell you nothing. And those who know nothing will say anything."
But being vice-president is no longer something to be sniffed at.
Since 1945, five vice-presidents have become president - Harry Truman, Lyndon B. Johnson, Richard Nixon, Gerald Ford and George Bush senior.
There is nothing democratic about the selection process.
Democratic front-runner John Kerry will appoint whoever gives him the best chance of reaching the Oval Office.
Like any calculation that appears immensely complex, it may actually be very simple.
The difficult stuff is making it work.
There are many theories.
The favourite is the "balanced ticket" theory. Because he is from the North, John Kerry should pick someone from the South.
The obvious candidate for this is his former rival John Edwards.
Possible vice-president candidates
John Edwards - Former presidential candidate
Dick Gephardt - Former presidential candidate
Bill Richardson - Governor of New Mexico
John McCain - Republican senator
Bob Kerrey - Former senator
Kathleen Sebelius - Governor of Kansas
Tom Vilsack - Governor of Iowa
His immense political skills and his sunny charisma would be an obvious asset to the sometimes dour Mr Kerry.
The downside is that Mr Edwards would probably not deliver any southern states, not even his home of North Carolina.
The South is now so resolutely Republican, many strategists believe the balanced ticket theory is a waste of time for Democrats.
"While I think John Edwards has more political talent in his little finger than John Kerry has in his whole body, I don't know that as a running mate that makes much difference," an independent campaign analyst in Washington, Charles Cook, said recently.
"It's not obvious to me that he fixes any problem."
In fact, Mr Edwards' greatest asset to Mr Kerry may be not in South, but in the North.
Mr Edwards' brand of conservative Democratic politics would play well with blue-collar workers in the crucial swing states of the Great Lakes.
Dick Gephardt's edge is the swing state of Iowa
Southern Democrats like former US president Bill Clinton and Mr Edwards connect with conservatives in a way that Northern liberals like Mr Kerry often fail to do.
Another erstwhile rival
On that basis, maybe Mr Kerry should choose a different erstwhile rival.
Former presidential candidate Dick Gephardt has the advantage of actually being from a swing state.
His home state, Missouri, has supported the winning candidate in every presidential election - bar one - since 1900.
Mr Gephardt's weakness is that he is another Washington insider.
If Mr Bush can take Mr Kerry apart for spending 19 years in Washington DC, he would have even more ammunition with Mr Gephardt's 28 years.
Mr Gephardt is also not very charismatic.
Mr Kerry may like that because he won't upstage him, but a Kerry/Gephardt ticket might not be much of a crowd-pleaser.
An eye on Hispanic voters
Another theory is the ethnic minority ticket.
Hispanics are going to be heavily courted in this election because their growing voter power could deliver swing states like New Mexico and Arizona.
The governor of New Mexico, Bill Richardson, is half-Mexican and has made little secret of the fact that he would like to be considered.
His problem is that he comes with a lot of baggage from the Clinton era.
John McCain is not a Democrat - but he is a popular friend of Kerry
He tried to find Monica Lewinsky a job and he was in charge of the bungled investigation of Wen Ho Lee, the Taiwan born nuclear scientist alleged to have spied for China.
Outside the box
Finally, there is the 'outside the box' theory.
Pick someone whom no one expects, who may not deliver any particular state, but who bolsters the ticket in other ways.
Mr Bush's choice of current vice-president Dick Cheney falls into this category.
Names mentioned include Mr Clinton (there is nothing to stop a two-time president becoming vice-president, but could Mr Kerry bear to be outshone?) and even the television anchor, Tom Brokaw.
But most tantalizing of all is someone who is not even a Democrat - Republican senator John McCain.
Mr McCain is probably the most popular politician in the US at the moment.
He is admired by Republicans and Democrats alike.
He is a Vietnam veteran and a friend of Mr Kerry's.
When asked recently what he would say if offered, he replied: "Obviously I would entertain it," which prompted a mini-firestorm of speculation.
However, in all likelihood he was just playing - unable to resist the opportunity to goad the Bush White House.
Mr Kerry does not have to make his decision until the Democratic Convention in July, but he is likely to announce it well before then.
The battle between Mr Kerry and Mr Bush is already intense.
The negative advertisements are on the airwaves.
Mr Kerry is going to need a partner to help take the flak and to come out fighting sooner rather than later.
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