Moment of drama in marathon race

The US primary season began with warnings from experts that the process was a marathon not a sprint.

After it dragged on through the spring, we began to look for athletic analogies that conveyed more of the spirit of grinding attrition that characterised Campaign 2008.

The 50km Walk, for example, or even the Slow Bicycle Race.

After years of preparation and months of campaigning we are left with only one possible comparison.

The race for the Democratic nomination is a Wagner opera - the main characters are still compelling, and there are moments of genuine drama... but it is all going on a very, very long time.

For Pennsylvania Democrats, this is another of those moments of drama.

The state's primary comes so late in the US election timetable that in a normal year, the nominations are all sewn up by now.

Flurry of activity

But 2008, of course, is turning out to be an extraordinary year and Pennsylvania is now the latest in a long line of states whose voters believe they could deliver the decisive blow that will settle the battle between Hillary Clinton and Barack Obama once and for all.

So there is political energy in the air, and on the streets.

Clutches of Obama and Clinton activists gather at intersections through the city to wave banners and lobby passers-by.

Vans with crackly loudhailers weave through the downtown traffic - and volunteers work the phone banks and send out e-mails.

The politics of the new century overlaps with the politics of the old.

And it has been six weeks since the last primary in Mississippi - the longest gap between primaries since the whole thing started in Iowa back in January - so the general appetite for politics, which was becoming just a little jaded, is sharp once again.

The TV advertising is sharper in tone too, reflecting the souring atmosphere of a long, close race between two candidates who appear below the surface, to dislike each other with growing intensity.

I have picked out two from dozens to show how it is possible to be negative, without being strident.

The Obama advert "He's got what it takes" lists precisely the kind of qualities and attributes his campaign says Mrs Clinton lacks, without mentioning her by name at all. "She hasn't got what it takes" is the not-very-subtle subtext here.

And her moving account of her small-town childhood should be read in the context of the row over Mr Obama's leaked comments about people in such places "clinging" to guns and religion out of bitterness over their economic hardships.

"HE doesn't get you," says this advert, "but I do. "

Likeability matters

So much in modern politics is decided by a kind of sub-current of popular sentiment that slowly bubbles away below the surface of news events, and which gradually shapes the outcome of events without reference to any single spectacular event.

That sub-current has been drifting the way of Mr Obama - he has slowly come to seem the much likelier winner of the two candidates.

There are some practical reasons for this of course.

"There is the impression that she is hanging on in the hope that some bombshell will emerge from the Illinois senator's past to unseat him"

He has won more states than Mrs Clinton, more votes and more elected delegates.

Influential "super-delegates" - those party grandees who have a big say in the Democratic process - continue to declare for him.

Big-name Democrats without a vote (like the ex-senator from Georgia, Sam Nunn, and Bill Clinton's old buddy, Robert Reich) like him too.

But the bottom line is that Mr Obama seems more likeable than Mrs Clinton to many voters, and polls show that they find him more trustworthy.

One particularly damaging poll showed that more than 60% of American voters did not trust Mrs Clinton - a figure that would seriously call her electability into question.

Does a nebulous idea like "likeability" matter? The answer is yes, and for two reasons.

Firstly, and most obviously, in an age where voters get to know their candidates on TV, voters tend to make personal judgements about the candidates based on what sort of people they appear to be.

Secondly, likeability gives you the precious ability to ride out the occasional storms which are an inevitable part of this process.

Consider what happened on the way into Pennsylvania, during that long six week break.

Mr Obama was embarrassed by his close links to the pastor of his church in Chicago, the Rev Jeremiah Wright.

One of Mr Wright's sermons gave Mr Obama the title for his book The Audacity of Hope, but some of the others were more problematic, including as they did references to the "US of KKKA", and a suggestion that the 9/11 attacks were some kind of payback for American policies overseas.

There were links too - albeit more tenuous links - with Bill Ayers, who is now a respected academic in Chicago but who was a member of a violent underground movement called "The Weathermen" back in the 1960s.

The stories put Mr Obama on the defensive, and he gave his least-convincing and most uncomfortable television performance of the campaign so far when he was grilled about his relationships with the two men in ABC's most recent televised debate.

But they did not appear to dent his standing with his supporters.

When Hillary Clinton was proved to have given a grotesquely misleading account of her arrival in the Bosnian town of Tuzla as First Lady in the 1990s (she claimed she came in under sniper fire, but TV pictures showed her strolling around the airport), the effect was much more damaging - the story probably contributed to those high figures for untrustworthiness which are such a problem for her.

Blue-collar vote

We are familiar with the story of Pennsylvania from other states like Ohio.

The rust-belt runs through it, and working class communities are faced with the loss of jobs in traditional manufacturing industries.

Before the campaign started we were told this kind of place, full of blue-collar Democrats, was Clinton country and for a long time she did indeed hold a double-digit lead here.

Mr Obama though, has slowly whittled that away - not least because his internet fund-raising has proved so much more effective than her old-fashioned political machine that he has been able to spend twice as much as her on TV advertising in Pennsylvania.

Certainly, here in Philadelphia it is hard to have the TV on for five minutes without seeing him.

It remains likely that Mrs Clinton will win Pennsylvania, but her problem is that she needs a resounding victory to persuade her financial backers, and the leaders of the Democratic Party, that she can still overhaul Mr Obama.

She will probably do well enough to persuade herself and her team that it is worth going on to Indiana and North Carolina.

The problem is that she is not really denting Mr Obama's lead in the polls and increasingly there is the impression that she is hanging on in the hope that some bombshell will emerge from the Illinois senator's past to unseat him.

There is no sign of that, but no sign either that Mrs Clinton has any other strategy for victory.