Jimmy Carter, a Libra with Libra rise and a Cancer midheaven, is the only President I know of who left the presidency and devoted himself to a life of service. Looking at his chart, Venus in Leo is his chart ruler, conjunct Neptune in the 10th house. The North Node (where one is headed) is also part of this conjunction.
Venus conjunct Neptune can mean many things. It can mean you fall head over heels in love (he did), it can mean you are attracted to people with alcohol issues, it can mean you love to sail (he went to the Naval Academy and was posted to sea). When the conjunction falls in the 10th house it can mean you devote yourself to helping the poor, as Carter did. He worked for many years for Habitat for Humanity, building houses for those in need. He also founded the Carter Center which works to advance human rights. This is a type of pure love that C.S Lewis wrote about in his book The Four Loves. He describes this love as unconditional God love, or agape, or charity. It is the very best use of Venus Neptune. Note also that his Venus Neptune in Leo is opposite Mars in Aquarius in the 4th house. His Aquarius Mars is stationary, so very strong. Aquarius is the people so it is fitting he worked for the people. Most U.S. Presidents have Saturn strong in their charts, and Carter does have Saturn in Scorpio conjunct his Ascendant. He also has a grand trine in water, Pluto in Cancer, trine Moon in Scorpio, trine Uranus in Cancer. Compassion. Some might find his sun in the 12th house an odd placement for a president, but those born with sun in the 12th house do well in institutions, and the U.S. Government is the ultimate in institutions.