Tomorrow's Democratic contests in Ohio, Texas, Rhode Island and Vermont are the most critical thus far. Most analysts expect that Obama wins would force Clinton out of the race. For Clinton, quite what a 'victory' would amount to is unclear and under debate, and both camps are happily playing down expectations with the intention of then exceeding them.

My own view is that Rhode Island and Vermont are sideshows, and that Clinton needs to win the popular vote in both Ohio and Texas in order to remain a credible factor in the race - an Obama victory in the popular vote in either state would make it hard to continue (I would expect a Clinton withdrawal on Wednesday should that happen). Current polls suggest this is possible, although the momentum is undoubtedly in Obama's favour: in both states he has eaten into if not overturned what a couple of weeks ago were double digit leads in both states. 

Complicating this situation is that the Texan method of apportioning delegates (a peculiar combination of caucuses and primaries, combined with heavily gerrymandered districts) favours Obama. A narrow popular vote victory for Clinton would probably give Obama a majority of the delegates. Given that Clinton's ultimate task is to overtake Obama in the number of delegates at the convention, a popular vote victory but delegate defeat could - in terms of securing the nomination - be as damaging as a popular vote defeat. Whether it would play that way in the media is another matter.

My prediction: Clinton wins in Ohio and (narrowly) Rhode Island, while Obama takes Texas and Vermont. Clinton then bows out magnanimously on Wednesday...

On a different note, I wrote an article for Comment is free about the potential impact of the presidential election on abortion rights in the US. It's available here.