Hillary Clinton promised last week to throw the “kitchen sink” at Barack Obama and it worked. Perhaps the most important number behind Mrs Clinton’s upset victories in Ohio, Texas and Rhode Island on Tuesday was the high proportion of late deciders who went in her favour. More than two-thirds of voters in Ohio and well over half in Texas who made their choice in the preceding 72 hours opted for Mrs Clinton.

One of the Clinton campaign’s key lessons for the remaining 16 nominating contests is that negative politics still works. In the week building up to the 4 March primaries the Clinton campaign hit Mr Obama repeatedly on a number of fronts.