This archaic vocabulary and these contractions are Tennyson's attempts at regularizing the cadence of the lines into iabic feet at first reading, so that the reader does not mistake such constructions as "flush'd" and "dew'd" as two-syllable words (flush-ed and dew-ed). The same thinking went into "clomb" (vs. climb-ed). Poetry was ready to go into its unrhyming phase (modernism). There were social and economic changes going on, also, that separated Romanticism from Victorian (for lack of a better term). Tennyson was also being influenced by German greats such as Goethe and Lessing. "Idylls of the King" is a blank verse work many consider his best contribution.