On the other end of the spectrum, four senators — Ted Cruz, Heidi Heitkamp, Tim Kaine, and Angus King — have each seen only one bill they've sponsored or cosponsored become law. Of course, the uniting factor is that they've all been in office for less than two years and, as with most of these metrics, it's skewed against rookie senators because they've had less time and don't have the seniority to see their bills become law.
This metric also benefits younger Democrats — who served when their party had a majority in both houses and the White House — and veteran Republicans, who had an advantage during the George W. Bush years. Put simply, it's a lot easier to get bills passed when the tracks are greased.
Longevity also plays a large factor. Each of the top 10 lawmakers has served in Congress for more than 30 years — since 1983 or earlier. Sen. Thad Cochran (who ranks in second on our Top 10 list) has served in Congress since 1973 — five years in the House of Representatives and 35 years in the Senate. On the reverse, Sen. Edward Markey joined the Senate in 2013, but served 37 years in the House before then.
Working on a prestigious committee (or being Senate majority leader) also entitles you to shovel a lot of legislation through the pipeline. Along with former Sen. Arlen Specter, Hatch, and Sen. Patrick Leahy have taken turns chairing the Senate Judiciary Committee since 1995. Similarly, Sen. Carl Levin has traded off his chairmanship of the Senate Armed Services Committee with former Sen. John Warner since 2001. But just because a bill passes through your committee and reaches the Senate floor, that's no guarantee it will become law.
Despite coming in ninth on the list, Leahy was less than thrilled about the ability for the current Congress, which has become intractably gridlocked, to pass laws.
"There was a time when bipartisanship was the norm in the Senate. We came together, made reasonable compromises, and passed landmark legislation to fight discrimination, protect victims of crime, support American jobs and protect the most vulnerable among us," Leahy said in a statement to National Journal. "I have always sought bipartisan support for my legislative priorities, from annual appropriations bills to patent reform legislation, and from post-9/11 laws like the USA PATRIOT Act to such monumental initiatives as the Innocence Protection Act. Reaching across the aisle should be and still can be a pathway to success in the Senate."
Levin, who came in third on National Journal's list, was less outspoken. He declined to comment on his legislative record, but Sen. Jack Reed praised Levin's work.
"Part of what makes Senator Levin such a skillful, effective legislator is he is smart, tenacious, and principled but still willing to compromise and work on a bipartisan basis to get things done," Reed said in a statement to National Journal. "He is someone who carefully studies the issues and always shares the credit."