Two months ago, the website added an official Congress channel, inviting Democrats and Republicans to share quirky political messages with voters. But analysts say the move has been hampered by politicians’ inability to adapt to an online audience. Andrew Rasiej, founder of the political technology site Personal Democracy Forum, said too many messages consist of warbling monologues that miss the point. Other postings, including one by Nancy Pelosi, Speaker of the House, were said to be too eccentric or random to resonate. In a minute-long video, Mrs Pelosi showed footage of her life behind the scenes in the Capitol Building...