Based on the timeline, I don't think there's going to be much substance to the charge of plagiarism that Hillary Clinton is leveling at Barack Obama.
Clinton communications director Howard Wolfson, during a conference call with reporters, pointed to a speech Obama delivered at a Democratic Party dinner in Wisconsin Saturday that lifted lines from an address given last year by his friend, Massachusetts Gov. Deval Patrick.
The Associated Press reported in January that Obama had borrowed ideas and speech points from Patrick, often without attribution. But with Obama now leading in the race for the Democratic presidential nomination, Clinton's campaign is using this example in an attempt to chip away at the premise of his candidacy.
If this information has been out there since January, then there's only one reason why the Clinton camp has held it for so long: they've done the research and couldn't find any more examples of plagiarism by Obama. If they had more than one arrow in their quiver they would have been shooting them for weeks, not saving it up for the news cycle before the March 4 primaries in Texas and Ohio.
That said, Obama's mis-step highlights once again his inexperience and naivity. Will this plagiarism swing enough votes to let Hillary win in Texas and Ohio, as she needs to do to save her candidacy? Who knows. It won't swing any black voters, but it might dampen enthusiam among his supporters. I'll be very surprised though if further research at this point turns up more instances of stolen words.