Arthur Goldhammer writes succinctly in The American Prospect that:

Sanders enjoys the advantage of purity. His hands have never touched the sausage mix, while Clinton is in it up to her elbows. No big banks were queuing up to offer Bernie whopping speaker’s fees, but then why would they? Power corrupts, but purity comes easily to those who until now never sought power but wished only to represent a neglected and undervalued point of view. There is honor in keeping faith with conviction, but purists and pragmatists cannot be judged by the same standards. “There is no king,” Shakespeare wrote, “be his cause never so spotless … can try it out with all unspotted soldiers.”

To wit, this is the problem with protest movements that seek to reform the political system by entering that system. They can only remain pure for so long before they are forced to compromise or break a promise to their supporters. Senator Bernie Sanders appears to be running a perfect progressive platform – a strong (almost singular) focus on wealth and income inequality, increasing the affordability of college, and increasing transparency in politics.

Senator Sanders regularly attacks Democratic frontrunner, Secretary Hillary Clinton, as not being a ‘real progressive’, generally drawing on her past vote in favour of the Iraq War, her paid speeches to bankers on Wall Street, and her ‘vacillating’ on the Trans-Pacific Partnership and the Keystone Pipeline. These attacks have played well to the election rallies as Sanders begins to look capable of mounting a formidable challenge to Clinton in the early voting states.

Until recently, Sanders was not taken seriously by the ‘inside the beltway’ media.  The most serious epithet (in American terms) that could be levelled at him is ‘socialist’, a term that he wears proudly. It is his public image on the campaign trail as straight talking, uncompromising, scruffy grandfather-type figure that wins him accolades. His blistering statements on income inequality, healthcare, and money in politics are red meat to his stridently liberal base. But his record in the House and Senate speaks to less of a fire-brand politician than is popularly believed.

Politico notes that Senator Sanders took to the floor of the Senate in 2010 to rail against an extension of the so-called ‘Bush tax cuts’, but two years later he voted in favour of a tax and budget bill that made 98 percent of those same tax cuts permanent. During the period 2001 – 2010, Sanders voted with the Democratic Party 95 – 99 percent of the time. According to the government tracking site OpenCongress, Sanders votes most often with Democratic Washington State Senator Maria Cantwell (who votes with her party 93 percent of the time).

None of this is to say that Senator Sanders’ is running an unworthy campaign. New York Governor Mario Cuomo famously remarked “You campaign in poetry. You govern in prose.” Senator Sanders’ rhetoric is clearly having an impact; he is running a surprisingly successful campaign. In this respect, Senator Sanders’ campaign bears a great deal of similarity to the 2008 campaign of then-Senator Barack Obama. Obama was criticised for using high style rhetoric in his pursuit of the White House, leading progressives to be disappointed by his compromises with a Republican controlled Congress.

The United States’ political system is set up to conflict at almost every level. As evidenced by the past 5 years, prolonged partisanship effectively paralyses the Congress and causes an unnecessary amount of domestic and international turmoil.

Over and over, Sanders has said that the only way he will succeed is if there is a “political revolution” within the United States. This largely insulates Sanders from failure, allowing his platform (and him) to remain ideologically pure. The key point is that Sanders the fire-breathing presidential candidate is different from Sanders, the benign Senator from Vermont.

For outsiders, the gap between rhetoric and reality is often difficult to discern, and an experienced politician like Sanders would have no trouble blurring the lines. In an age of perfectly curated social media profiles and filtered Instagram pictures, purity is a valuable commodity. Like any resource, the value is in its (seeming) scarcity.