Actually, I just researched it. Kennedy and Harding are the ONLY two Senators directly elected President. 15 other former Senators became President, but just these two ever moved directly from the Senate to the White House.
Monroe, Quincy Adams,Jackson, Van Buren, William Henry Harrison, Tyler, Pierce, Buchanan, Andrew Johnson, Benjamin Harrison, Truman, Lyndon Johnson and Nixon all served in the Senate. But were out of the Senate when elected. We are on our 43rd Presidency now. 2/43 shot of a sitting Senator winning. I like me them odds.
When bush 41 was running in 1988, all the talk was about how no sitting VP had been elected to pres since JQ adams.