The most recent candidate under the DNC banner is Lincoln Chafee who interestingly, besides being the lone Republican (he switched parties) to vote against the Iraq war, is vehemently pro-metric system [politico.com]. I remember when I was a kid, the freeway signs [wikipedia.org] for distance and speed printed in both English and metric. Converting all those signs from miles to km (again) would cost money, but then, using the English measurement system costs money too, forever -- according to a random guy I googled up without putting any real effort into it because I'm not that interested in proving myself wrong (Paul Naughtin [themetricmaven.com]), somewhere between six billion and a trillion [themetricmaven.com]. There are without a doubt, critics who might call that somewhat of a wide margin but as one witty commenter noted: [stackexchange.com] "It is probably impossible to give an upper bound on that, however I can give you a lower bound: 500 Million Dollars for the loss of the Mars Climate Orbiter by NASA".
Now, I'm a firm neither GOP nor DNC voter ... but I'm tempted.