To date, sixteen senators have also served as president of the United States. Three senators, Warren G. Harding, John F. Kennedy, and Barack Obama moved directly from the U.S. Senate to the White House.
(Photo: Warren G. Harding. Senate Historical Office)
James Monroe
Senator, 1790-1794
President, 1817-1825
John Quincy Adams
Senator, 1803-1808
President, 1825-1829
Andrew Jackson
Senator, 1797-1798; 1823-1825
President, 1829-1837
Martin Van Buren
Senator, 1821-1828
President, 1837-1841
William Henry Harrison
Senator, 1825-1828
President, 1841
John Tyler
Senator, 1827-1836
President, 1841-1845
Franklin Pierce
Senator, 1837-1842
President, 1853-1857
James Buchanan
Senator, 1834-1845
President, 1857-1861
Andrew Johnson
Senator, 1857-1862; 1875
President, 1865-1869
Benjamin Harrison
Senator, 1881-1887
President, 1889-1893
Warren G. Harding
Senator, 1915-1921
President, 1921-1923
Harry S. Truman
Senator, 1935-1945
President, 1945-1953
John F. Kennedy
Senator, 1953-1960
President, 1961-1963
Lyndon B. Johnson
Senator, 1949-1961
President, 1963-1969
Richard M. Nixon
Senator, 1950-1953
President, 1969-1974
Barack Obama
Senator, 2005-2008
President, 2009- present
https://www.senate.gov/artandhistory/history/common/briefing/senators_became_president.htm
Most of them are/were Rats.