John Lewis to Clinton: 'Happy Birthday, Madame President'
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Rep. John Lewis (D-Ga.) wished former Democratic presidential nominee Hillary ClintonHillary Diane Rodham ClintonWoman behind pro-Trump Facebook page denies being influenced by Russians Trump: CNN, MSNBC 'got scammed' into covering Russian-organized rally Pennsylvania Democrats set to win big with new district map MORE a happy birthday on Thursday in a tweet calling her "Madame President."

Lewis's tweet Thursday afternoon had been retweeted more than 1,500 times less than a half-hour after it was posted.

Clinton won the popular vote for the presidency last November, but lost the White House to President TrumpDonald John TrumpAccuser says Trump should be afraid of the truth Woman behind pro-Trump Facebook page denies being influenced by Russians Shulkin says he has White House approval to root out 'subversion' at VA MORE in the Electoral College.

Lewis, a civil rights icon, endorsed Clinton and campaigned on her behalf. His tweet followed others from fellow prominent Democrats, including Clinton's husband, former President Bill ClintonWilliam (Bill) Jefferson ClintonShould the Rob Porter outcome set the standard? Make the compromise: Ending chain migration is a small price to legalize Dreamers Assessing Trump's impeachment odds through a historic lens MORE.

Clinton, who turned 70 on Thursday, is currently touring the country as part of a national book tour for her memoir, "What Happened." The book examines the 2016 election and Clinton's eventual defeat to Donald Trump.