This one seems a little shaky. It isn't really Hooker's view, but the author's James Clement Ambrose, who quotes a letter from Hooker in which Hooker praises Ambrose to the skies.
The difficulty is the article is from 1884, years after Hooker's death, and a year before Grant's for that matter, and Ambrose was writing for the Chicago Times, the leading Democratic paper during the campaign of 1872, which he claims for the date of this exchange of letters. He writes a lot of incentive about Grant, and claims Hooker's approved it all.