By Richard Allen Greene
BBC News, Washington
Veteran Democratic Senator Chris Dodd threw his hat into the 2008 presidential race this week.
Mr Dodd might seek advice from his colleague John Kerry
He joins a field that includes former Senator Mike Gravel, former House armed services committee chairman Duncan Hunter, and former Governors Tom Vilsack and Tommy Thompson.
Outside Washington, all these men are likely to elicit exactly the same reaction: Who?
In the capital, the question would probably be slightly different: Why?
Americans will not decide who replaces George Bush in the White House until 4 November 2008, but the number of likely winners is already shrinking.
For the Democrats, Hillary Clinton has been sweeping up the money and sits on a war chest in the tens of millions of dollars - and she has not even announced that she is running.
Neither has fresh-faced Senator Barack Obama, who has generated incredible buzz, apparently off charisma alone.
Obama's December trip to New Hampshire put the spotlight on him
Former vice-presidential candidate John Edwards - who has said he is running - seems the only Democrat who could plausibly take the nomination away from the front-runners.
The situation is similar for the Republicans.
Senator John McCain has tied up money, endorsements and talent.
Former New York Mayor Rudolph Giuliani has name recognition, connections, and hero status.
Former Massachusetts Governor Mitt Romney has good looks, fundraising ability and - potentially - a solid right-wing constituency.
'Best for the job'
So why do respectable but obscure figures think they have a chance at the White House?
Anita Dunn, a strategist who worked with unsuccessful presidential contender Bill Bradley in 2000, says many people run because they genuinely believe they can do the job better than anyone else.
"Never neglect the idea that they might think they are better qualified, have a better vision, and think they are the best person for the job."
Mr Carter's unexpected victory continues to inspire hopefuls today
At least one figure has risen from complete obscurity to become president in living memory - and he inspires long-shot candidates, she says.
"Their patron saint is Jimmy Carter, who ran against better known, better funded candidates and won" in 1976.
Hank Sheinkopf, a consultant who has worked on hundreds of campaigns at all levels, including Bill Clinton's 1996 re-election effort, says some contenders simply decide to roll the dice.
Call it "a very American: Why not?" he says.
There are a number of reasons for a long-shot candidate to go for it, he says.
"Lightning could strike - you could get nominated. You could get nominated for vice-president, or you could get enough delegates to be a dealmaker, or there might be a deal to get you out.
"Sometimes they are hopeful they could get time on television," he adds.
Message for the medium
That can be a strong motivation for some "message" candidates, who run more to highlight issues than in hopes of winning.
Former Alaska Senator Mike Gravel - whose own website's top item is an article calling him a long shot - may fall into that category.
"I am a candidate for the presidency because America has lost its moral compass," he told the BBC in a statement.
Message candidates like Mr Kucinich may have more fun than most
"War, including the war in Iraq, represents an expression of failed foreign policies. We need to return to the path of co-operative diplomacy."
Message candidates - also including anti-war congressman Dennis Kucinich, who is making his second bid - may be among the few contenders who actually enjoy a presidential campaign, Anita Dunn says.
"They don't have high expectations. They have the liberation of being able to say exactly what they think," she says.
Top Democratic strategist Donna Brazile says she likes campaigning for long-shot candidates.
"I enjoy working for 'asterisks' - unknown candidates with limited campaign support and appeal. They have more fun and are willing to take some risks."
But most candidates do not enjoy the rigours of the campaign, experts agree.
"It is not fun," Mr Sheinkopf says bluntly.
"It is arduous work, raising money, shaking hands with people you don't want to be with, knowing that if you are a second-tier candidate you are not going to get into the papers."
Given those drawbacks, even an insider like Mr Sheinkopf admits that sometimes it is a mystery why a particular individual decides to run:
"There is no explanation sometimes for the sense public officials have of themselves."