The guilty verdict will complicate not only his re-election bid but also the remainder of his current term in the Senate. His colleagues have the option - never exercised - of voting to expel him before his term ends in January. Four U.S. senators have been convicted of crimes, historians note, but not one has received a presidential pardon.
The other four Senators being: John Hipple Mitchell (R-Oregon, 1905), Joseph R. Burton (R-Kansas, 1906), Truman H. Newberry (R- Michigan, 1920) and Harrison Williams (D - New Jersey, 1982). When Newberry and Williams were convicted, the presidents (Woodrow Wilson and Ronald Reagan) were from the opposite party. The Mitchell and Burton convictions came during a Republican administration. But the Republican was Theodore Roosevelt, who may not have been too saddened to see them convicted! Indeed, Roosevelt described Burton as a "higher up" who "swindled on a large scale." See Herald story here.
In sum, PardonPower is not certain why Senatorial status would be (or is) a particularly relevant factor. Consider these pardons: 1871 - Rep. C.C. Bowen (R), pardoned by Ulysses S. Grant (R); 1928 - Rep. John W. Langley (R), pardoned by Calvin Coolidge (R); 1933 - Rep. Francis H. Shoemaker (L), pardoned by Franklin Roosevelt(D); 1947, Rep. James M. Curley (D), commutation of sentence granted by Harry Truman (D); 1950 - Rep. James M. Curley (D), pardoned by Harry Truman (D); 1952 - Rep. Andrew J. May (D), pardoned by Harry Truman (D), 1952 - Rep. James P. Thomas (R), pardoned by Harry Truman (D); 1965 - Rep. Frank Boykin (D), pardoned by Lyndon Johnson (D); 2000 - Rep. Dan Rostenkowski (D), pardoned by Bill Clinton (D); 2001 - Rep. Mel Reynolds (D), commutation of sentence from Bill Clinton (D).
* Note: The Editor is aware of no authoritative list of pardons granted to members of Congress (former or current). The above information was gleaned from a quick scan through original data on presidential pardons from 1789 to 2008.