AS DEMOCRATS prepare for yet another gruelling round of primary campaigning following Hillary Clinton's victory in Pennsylvania, many are asking: "Why can't Barack Obama finish her off?"
Ahead in delegates and awash with money, Mr Obama's campaign was unable to curtail the challenge from Mrs Clinton, who beat him by ten points in the last big-state primary on Tuesday.
She won by holding onto the same core constituencie
s who have got her through the race so far: women, the elderly and rural and blue-collar voters.
"Working-class voters in swing states are going to be crucial (in the presidential election]," says Philip Klein of the American Spectator. "(Obama] just hasn't been able to make enough headway among those voters."
Mrs Clinton has held onto these supporters despite being outspent 3-1 in advertising by an Obama campaign that hit Pennsylvania with all the razzmatazz that characterised his earlier campaigns. She insisted yesterday that this success showed that "the tide has turned" and promised to make further inroads into Mr Obama's delegate lead in the nine smaller primaries that remain.
Then, she hopes, she can convince the all-important party-appointed superdelegates that she would do better against Republican presidential candidate John McCain in November, despite trailing Mr Obama in the popular vote.
The robustness of her core voters gives her a powerful argument. These blue-collar voters are the ones nicknamed the Reagan Democrats after they defected en masse for Ronald Reagan when he beat Jimmy Carter in the 1980 presidential election.
A powerful 28 per cent have told pollsters they are willing to defect again, saying they will vote for Mr McCain, not Mr Obama, if Mrs Clinton does not win the Democratic nomination.
And it is unclear what more Mr Obama can do to win these voters, a cause that probably suffered through remarks earlier this month about "bitter" small-town America.
Mrs Clinton still has a mountain to climb.
First, she has no realistic hope of beating Mr Obama in what remains of the primary race. And if Mr Obama wins more states, more voters and more delegates, failing to give him the nomination risks tearing the party apart.
For just as Mrs Clinton scores big with blue-collar workers, so Mr Obama has energised two constituencies at the very core of Democratic success: African- American voters and the young.
The fight is also confusing many Democrat voters.
"Part of me wishes someone would just pull ahead definitively," said Karen Sherman, 41, a teaching assistant from Kentucky.
"The way they are going they are both the underdog to McCain," said Ken Corbus, 65, a self-employed businessman.
Meanwhile the New York Times, which had previously endorsed Mrs Clinton, yesterday ran an editorial criticising her for a negative campaign that it says may turn away Democratic voters. "The negativity, for which she is mostly responsible, does nothing but harm to her, her opponent, her party and the 2008 election," the newspaper said.
Many think Mr Obama's best course is to do nothing – simply hold onto his lead and let the rest of the race play out.
By the end of the contest he is likely to have about 1,900 delegates, at which point he will need only 125 of the remaining 311 superdelegates to give him an absolute majority.
Those 125 may not even wait until the end of the primary contests: the past month has seen more than 80 "supers" flock to Mr Obama and if this continues, he may find himself carried over the finish line before the final primaries in June.
The full article contains 608 words and appears in The Scotsman newspaper.