A capacity crowd on the scale of a Manchester United home game turned out in Oregon on Sunday to see Barack Obama speak ahead of this week’s primary. It has been widely reported that he focused almost exclusively on Republican nominee, John McCain, and barely mentioned Hillary Clinton. He is already spending time visiting general election swing states while the US media have already declared game over. So what has Clinton achieved by staying in it?

There are four theories. The first is that she is attempting to destabilize Obama’s campaign to give herself the best shot of running in 2012. By repeatedly talking about Obama’s inexperience and lack of substance, the theory goes, she will write McCain’s election script and hand him victory. After three defeats in a row, there would not be a single Democrat in the country who would begrudge her a chance next time.

Second, some suggest she is angling (and should be given) the vice-presidential nomination. By winning blue-collar states like Pennsylvania and Ohio, she has shown that she can help secure the presidency. The ‘dream ticket’ is popular with voters and especially with some Democrat bosses who fear Clinton supporters staying at home if Obama wraps up the nomination. In this role she could work diligently on healthcare reform and other pet projects while leaving the high-level foreign policy and economic brief to Obama.

Third, there is the possibility that she wants to take the position of senate majority leader from Harry Reid. Whatever happens in the presidential election, the Democrats are widely expected to increase their majorities in both houses of Congress. The jury is out on Reid’s performance since the midterm election and Clinton’s ongoing display of gutsy determination may be enough to convince her colleagues that she is perfect for this key brokering role.

Finally, she may just believe she can win. Although Obama is only 115 (out of over 4000) delegates away from winning, he is unlikely to get this before the Democratic National Convention meets in late August unless Clinton pulls out. The five remaining primaries will not prove conclusive and there is little incentive for the roughly 200 undeclared superdelegates (party bigwigs who get 20 per cent of the Convention vote) to show their hand now when their leverage for plum positions will only increase.

So working on the basis that Clinton stays in the race until the convention, what could show up? On 31 May, a meeting will decide whether to give the 313 delegates from Michigan and Florida a vote at the Convention (currently banned because those states flouted election rules). Their inclusion would pretty much erode Obama’s current lead. Although he appears to have seized the initiative after a very poor April, Obama may face further embarrassment over his personal ties to rogue priests and slumhouse swindlers.

Finally, if Clinton demolishes Obama in Kentucky and Puerto Rico while holding her own in Montana, South Dakota and Oregon, she may just be able to claim a majority of actual votes. This would belittle Obama’s argument that superdelegates should vote with the majority from the primary election. However unlikely this scenario may seem, there have been enough twists and turns in this election not to be certain of anything.