A persistent theme in the Democratic primary contest is that the race is between Hillary Clinton, the pragmatist, and Bernie Sanders, the purist – images that the candidates have both acquired and themselves actively nourished.

Clinton has referred to herself as a "progressive who gets things done," and Sanders, who is proposing large and expensive government programs in the realms of education, healthcare, infrastructure, and energy, has appropriately declared that his campaign is about "thinking big, not small."

Yet the extent of the candidates' pragmatism or purity is not mere rhetoric incapable of being measured; it is, in fact, quite quantifiable. Both candidates have served in Congress and thus have experience trying to "get things done." Hillary Clinton served in the Senate between 2001 and 2009, and Bernie Sanders served in the House between 1991 and 2007 and has served in the Senate since 2007.

So, when it comes to their legislative records, how productive have they been?

According to Jeffrey Lazarus's analysis in the Washington Post, Clinton sponsored 10 substantive bills (excluding symbolic legislation such as the renaming of a federal building and co-sponsored bills) that were approved by the Senate. Sanders, by contrast, steered zero substantive bills through the House and only one through the Senate.

By this metric, Lazarus declares that Clinton was the more effective legislator (though none of these 10 sponsored bills became law, whereas Sanders' lone bill did). Yet the exclusive focus on sponsored bills ignores an important aspect of legislative effectiveness: the passage of proposed amendments.

During her time in Congress, Clinton passed zero roll call amendments (amendments whose passage is determined by recorded votes rather than voice votes). Sanders, on the other hand, passed 21 roll call amendments.

Indeed, Sanders has been dubbed the "amendment king" for his successful passage of 17 roll call amendments between 1995 and 2007 – a record for those who have served in the House. This accomplishment is especially noteworthy given that during this period, Sanders served as a politically independent democratic socialist in a House led by a Republican majority.

While it is tempting to regard amendments as legislatively inferior to bills as a rule, some of the amendments proposed by Sanders in the House have had an outsized policy footprint. In 2001, he made major changes to two appropriations bills: one amendment prohibited the importation of goods made by forced or child labor, and another set aside $100 million in federal funding for community health centers.

In the House, Sanders regularly formed pragmatic ad hoc alliances to garner support for his proposals. One former aide to libertarian congressman Ron Paul noted the Sanders was at times an effective ally, since Paul and Sanders tended to "have a lot in common" because both were "frustrated by the same obstacles in the system."

Indeed, it was Sanders who managed to have an amendment passed in the Senate that accomplished what Rep. Paul failed to achieve for years: an audit of the Federal Reserve. Though Sanders' amendment was only focused on the period between December 2007 and July 2010, the audit uncovered the Fed's delivery of $16 trillion in low-interest loans to major financial institutions – loans that added $2 trillion to the money supply.

Sanders forged cross-aisle coalitions in the Senate to muster support for other significant amendments as well. Supported by Republicans like Sen. Charles Grassley, for instance, Sanders passed an amendment to ensure that bailed out institutions did not hire foreign workers over American workers.

Moreover, Sanders passed amendments attractive to anti-cronyism conservatives, including one amendment designed to expose the revolving door between the Pentagon and defense contractors, and another preventing the taxpayer-supported Export-Import Bank from funding the construction of nuclear power plants in China.

Sanders was also instrumental in shaping and passing the bipartisan Veterans Affairs reform bill of 2014. For his efforts, he drew praise from Sen. John McCain, who commented, "I’ve worked with people who tell you they are going to do one thing and then do another, and Bernie did what he said. And he was very effective. ”

But not every congressional colleague has seen Sanders as an effective legislator. Former Democratic U.S. Representative Barnie Frank, who supports Hillary Clinton, has said that Sanders "plants his flag and expects that someday everyone will see he was right.”

It is this version of Sanders, who has staked out positions well to the left of Clinton and the Democratic Party during his campaign, that is most familiar to the American public. Indeed, Clinton has campaigned on the impression that Sanders lacks the political capital and prowess to get his proposals passed and has portrayed herself as the Democratic candidate who can deliver on her promises.

"I am concerned that some of his ideas just won't work, because the numbers don’t add up. Others won’t even pass Congress, or they rely on Republican governors suddenly having a conversion experience and becoming progressives," she told a union audience, adding, "In a number of important areas, he doesn’t have a plan at all."

In response to the claim that a Sanders administration would be a stubborn and impotent one, Sanders, who admits to not liking to talk about himself, has referred not to his legislative past, but to the future and to the necessity of a grassroots "political revolution" that will drastically alter the composition and priorities of Congress.

Despite his reluctance to talk about himself (or even speak in the first-person), it is still unclear why Sanders has downplayed his talent as a political maneuverer: perhaps it is to retain his status as an anti-establishment "outsider," or in order to avoid mentioning his collaboration with conservative Republicans while seeking the Democratic nomination – a message that would be more palatable to a general election audience.

But regardless of his campaign persona as a naive idealist and purist who would be incapable of working with a divided Congress, Sanders' record as a legislator is nevertheless largely one characterized by transpartisanship and principled compromise.