The "plagiarism" flap over Barack Obama is bogus and overstated. It makes me think worse about whoever is pushing this complaint, rather than about Obama himself.
Conceivably Obama would have been wiser to introduce his recent discourse on the role of "hope" by saying, "As my friend the governor of Massachusetts has often pointed out...." But please: A candidate on the stump utters tens of thousands of words every single day. Few of those can be "original" in any deep sense. For many of the words, even the most brilliant candidate relies on help from people whose job is to think of newer and better ways to make the campaign's point.* We should be suspicious of candidates who don't seek this kind of help; it suggests that they are naive about the tradeoffs, triage, and delegation necessary to run a campaign well, let alone an Administration.
The classic campaign stump speech, in its low-rent version, is a memorized mish-mash of things the candidate has already said. In its high-rent version, it's an improvised and steadily evolving mish-mash of things the candidate has already said -- but slightly retuned with each delivery, to reflect the news and the location and the latest charge and countercharge. It's also slightly altered or enriched with each delivery, to include the latest anecdote or aphorism or snappy phrase or moving line that the candidate, or someone around him, has come across that might help push the campaign's main theme. Unless a candidate is a total robot, giving the very same speech time after time, he or she is inevitably grabbing whatever idea, illustration, or phrase is at hand. Again, not to do this is to suggest that a presidential candidate is not quite ready for the job.
Moreover, on the specific Patrick/Obama point at issue: it's not as if no one had thought of this argument (about hope and inspiration), or these examples -- FDR, JFK, MLK Jr -- before Deval Patrick uttered them. Speechwriters could hardly exist without this theme or these illustrations!
Talk about American resolve in the dark days, and you're going to talk about Lincoln and FDR -- plus George Washington at Valley Forge, if you have a little more time to fill. Talk about American national ambition, and you're going to talk about the westward movement across the frontier and the Apollo Project's race to the moon. Talk about American opportunity, and you're going to talk about the GI Bill. Talk about American resolve and determination, and you're going to talk about Pearl Harbor and the fall of the Soviet regime. Talk about the power of ideas, and... [take the home speechwriter-aptitude test! Fill in this blank. One possible answer explained here.]