Washington ( CNN ) -- Long before computers or televisions existed , a man who would become a U.S. senator and then president started an affair with his neighbor 's wife . Even telephones were relatively new back then , so Warren Harding wrote Carrie Phillips smoldering love letters during their 15-year relationship that ended prior to his inauguration in 1921 . `` I love you more than all the world , and have no hope of reward on Earth or hereafter , so precious as that in your dear arms , in your thrilling lips , in your matchless breasts , in your incomparable embrace , '' said a 1910 letter first revealed in the book `` The Harding Affair '' by James David Robenalt . Snail mail . Almost a century later , the snail mail between Harding and Phillips becomes fully public later this month , revealing the most intimate secrets and thoughts of a man destined for the pinnacle of power as America endured the First World War . In his book , Robenalt examines the possible historical impacts of the affair , noting that Phillips may have spied for Germany and influenced Harding against running for president in 1916 as the war approached . `` The Harding Affair '' `` There 's that sex steamy side to these letters , '' he told CNN in an interview Monday . `` But there 's also the big question of whether the United States should get involved in the First World War . They really debated that back and forth . She was really pro-German , he was very pro-American . '' Of equal interest , especially in the modern era of celebrity scandal mongering , is the pure salaciousness of the letters ' content . `` They really are very graphic love letters , '' said Robenalt , who came across them while researching his 2009 book . `` And people think that 100 years ago nobody had sex fantasies and I keep telling people if those people did n't have sex fantasies , we would n't be here today . '' Keeping such a secret seems impossible in today 's digitally monitored world . Not so back in 1905 , a decade before the first coast-to-coast long distance phone call . Salacious details . As outlined by Robenalt 's book , Harding was married at the time and serving as Ohio 's lieutenant governor . He recommended that his friend and neighbor Jim Phillips , Carrie 's husband , go to a sanitarium that spring to help recover from the death of their 4-year-old son a year earlier . Meanwhile , Harding 's wife Florence was recovering from a kidney disease . By August , Harding 's affair with Carrie commenced , though it only became physical three years later , according to Robenalt 's book . `` I do love you so , '' he wrote in 1913 , two years before his election as Republican senator from Ohio. `` I wonder if you realize how muchâ€ ” how faithfully , how gladly , how reverently , how wistfully , how whole-heartedly and how passionately . Yes , you do know the last , you must have felt the proof , but you ca n't know the others . '' The same letter also showed Harding 's concern about the affair being discovered , long before the Internet age . `` I have been thinking of all those letters you have , '' wrote , adding that `` I think you have a fire , chuck 'em ! Do . You must . If there is one impassioned one that appeals to you , keep it until you are tired of it , but chuck the rest . Why it frightens me to think I ever dared mail them to your address . '' By 1916 , circumstances had changed , according to another letter . From `` enraptured bliss '' to `` depths of anxiety '' `` It is a little more than thirty-six hours since I saw you , and they have all been given to you , amid the perturbation I could not shake off , '' Harding wrote after what Robenalt said was a secret visit to Phillips in Marion , Ohio . `` If you designed to punish me you have succeeded fully , '' the letter continued . `` I came with heart a hungering , I knew the flight to enraptured bliss , and was then suddenly plunged to the depths of anxiety . '' The problem ? Someone named Robinson , described by Robenalt as a rival lover , came to Marion . `` I had feared for a year , but would not surrender , '' Harding 's letter continued . `` I know now of my failure . I sought the impossible , and I am defeated . '' Robenalt noted the influence of the pending war at that time . `` He ultimately voted for war , '' the author said of Harding . `` He knew that it would probably ruin their relationship , and kill him politically in a state that had a lot of German-Americans . '' The affair ended four years later , as Harding ran for president in an election he won easily over Democrat James Cox . He did n't survive his first term , dying of illness in 1923 . In a recent statement , the Library of Congress announced it would make the more than 1,000 pages of love letters public on July 29 , with a discussion about them scheduled for July 22 in the Mumford Room of the James Madison Building in Washington . Photos : Presidential inaugurations and oaths through history . CNN 's Paul Steinhauser , Sherisse Pham and Kimberly Berryman contributed to this report .
Coming soon : love letters between Warren Harding and his mistress . The 15-year affair ended before Harding became president in 1921 . Hide Caption 1 of 10 Photos:Photos: A book on the affair examines its possible historical impact .