Krugman predicted austerity of 2013 would hurt. It didn't.
http://krugman.blogs.nytimes.com/2013/04/28/monetarism-falls...
http://econlog.econlib.org/archives/2014/01/the_parrot_is_s.... http://econlog.econlib.org/archives/2015/01/the_cbos_foreca....
Krugman predicted the sequester would cost 700,000 jobs.
http://www.nytimes.com/2013/02/22/opinion/krugman-sequester-...
I can't dig it up, but Sumner claimed it would not provided NGDP didn't fall (i.e., the fed caused a monetary offset). You'll never guess what happened next.