ABC’s George Stephanopoulos is taking the next step with Twitter, he writes in his blog, landing Sen. John McCain for a 140-characters-at-a-time “Twitterview” on Tuesday. Stephanopoulos is also encouraging readers to send him questions for the Republican via the microblogging format that’s recently become all the rage in Washington; the interview is scheduled for noon Eastern. (More George Stephanopoulos stories.)