U.S. Senator Bernie Sanders (I-Vt.) will officially announce his presidential candidacy, becoming the first candidate to challenge Hillary Clinton for the Democratic Party’s nomination.

Cognizant of the dissatisfaction Americans feel toward both major political parties, and aware of many progressives’ disillusionment with the Democratic Party, Sanders has long been reluctant to formally un-declare his political independence.

Yet before a crowd in Iowa in October 2014, he admitted that he would receive more media attention and greater access to televised debates if he chose to run as a Democrat. Likewise, he confessed, achieving access to ballots in all 50 states would have been a challenge as an independent.

Sanders’ political career as an outsider began back in the 1970s. After a number of failed attempts at winning a statewide office, Sanders was elected as the mayor of Burlington, Vermont’s most populous city, in 1981 -- ousting the six-term Democratic incumbent by ten votes.

As mayor, Sanders implemented changes to be expected from a self-described socialist in the tradition of labor leader and five-time presidential candidate Eugene Debs. He raised taxes, devoted more resources to municipal projects (even creating a volunteer program to help senior citizens with snow removal), and successfully fought for reduced rates for his citizens from the local cable provider.

He also secured funding for a “community land trust” – the first city in the country to do so – to make housing more affordable for some residents, a majority of whom were renters in the 1980s.

However, his administration cooperated with businesses as well. During his tenure, the city attracted the minor league baseball team, the Vermont Reds, and he befriended the developer and philanthropist Antonio Pomerleau, with whom he clashed at first over a waterfront project upon election.

Through securing more business loans and promoting community development projects, the city prospered: the U.S. Council of Mayors named Burlington the “Most Livable City in America” with a population under 100,000.

After four 2-year terms, Sanders was elected to the U.S. House in 1990 as Vermont’s sole representative.

Sanders is often described as an independent who caucuses with the Democrats. However, Sanders – the longest serving independent in congressional history – has a long record of being motivated by issues and principles rather than partisanship.

Ron Paul (R. – Texas) – to pass an amendment to a bill that denied $5 billion in loans from the Import-Export Bank to Westinghouse funding a project to build nuclear reactors in China.

In the same year, Sanders successfully sponsored a “Lockheed amendment” in the House to prevent a $1.9 billion contract to Lockheed Martin privatizing Flight Service Stations across the country. However, in the Senate, his version of the amendment was defeated when Democrats – following the lead of Harry Reid (D-Nev.) – opposed it.

Sanders continued his bipartisan, issues-driven legislating after being elected to the U.S. Senate in 2007. For instance, following the VA scandal, Sanders joined Sen. John McCain (R-Ariz.) in sponsoring a bill that called for the construction of 26 additional hospitals in 18 states and for $500 million to hire VA doctors and nurses. It also called for a remedy to long wait times by making it easier for vets to see private doctors and facilitating the process for firing VA staffers -- such as the administrators who were responsible for the deaths of 40 veterans because of perverse financial incentives.

Yet despite the occasional overlap and cooperation with members of Congress, Sanders has made it clear in recent years that his priority is to lead what he calls a "political revolution" in the country to defeat the influence that wealthy groups and individuals exert over elections, members of Congress, and public policy.

One plank of Sen. Sander's platform is campaign finance reform. In addition to repeatedly (and unsuccessfully) pushing for amendments (such as this one from 2013) to undo the effects of the Citizens United decision of 2010, Sanders also advocates for the public funding of federal elections.

Perhaps the most significant plank in his platform is combating wealth and income inequality, and reversing the trend of income distribution in the post-recession era, when approximately 99 percent of all income gains have accrued to the top one percent of earners.

Sanders has several major proposals for enriching the middle and working classes. First, he supports raising the minimum wage gradually to $15 an hour. Also, he supports empowering labor unions to negotiate for fairer wages and benefits, and he is in favor of creating, sustaining, and promoting new business models such as employee-owned cooperatives that give workers a greater say in the management of their enterprises.

Relatedly, he opposes the Trans-Pacific Partnership (TPP) that is currently slated for fast-track approval by Congress, citing growing trade deficits and job losses from previous free trade agreements.

Sanders calls the TPP and its predecessors – negotiated by and for corporate interests – "disastrous trade policies."

Citing the country's "crumbling infrastructure" (or "in-fra-struk-shuh" in Sanders' heavy Brooklyn accent), Sanders has proposed spending $1 trillion over five years to create millions of public works-style jobs. To pay for these projects, Sanders proposes making the tax code more progressive and closing loopholes that allow corporations to keep their profits offshore and untaxed -- starving the federal government of nearly $600 billion in revenue over the next decade.

Sanders also believes that funds for domestic spending can be found elsewhere in the budget. Sanders has been especially critical of the budget proposed by Senate Budget Committee Chairman Mike Enzi (R-Wyo.), which called for tens of billions of dollars in increased defense spending while reducing non-defense spending through major cuts to programs that help people with low and moderate incomes.

Given this critique of military spending, Sanders still recognizes the threat posed by radical Islam, and says ISIS needs to be defeated. He believes that America should be part of an international effort to defeat the group and that countries such as Saudi Arabia, which has the fourth most expensive military in the world, should lead the campaign against ISIS.

While certainly in favor of greater government spending and involvement in the economy, Sanders is an ornament of the left-libertarian tendency in American politics – one that combines a commitment to economic fairness with a commitment to protecting civil liberties.

Sanders, for instance, has long opposed intrusive government surveillance. He has attacked two legal pillars of abusive surveillance, including Section 215 of the PATRIOT Act and Section 502 of the Foreign Intelligence Surveillance Act (FISA). In 2013, following the initial Snowden revelations, Sanders proposed the Restore Our Privacy Act to limit overly broad requests to monitor communications and records and to expand reporting requirements and increase congressional oversight.

Sanders has also been a consistent proponent of gay and lesbian rights. He opposed the passage of the Defense of Marriage Act (DOMA) in 1996, which allowed states to not recognize same-sex marriages from other states and did not grant them equal protection under federal law. He supported Vermont's civil union law in 2000 and its legalization of gay marriage in 2009.

Sanders' entrance into the presidential race represents – as will be pointed out countless times over the next year – a deliberate attempt to pull the Democratic Party left. Even if he does not win the nomination – though he has stated he would not enter the race unless he believed he could win the presidency – his presence will no doubt force whoever the nominee is to address the issues that have created the ideological fault lines that separate independents, moderates, and progressives.

He may replicate what occurred during the mayoral contest in Chicago earlier this year. There, Jesus "Chuy" Garcia forced a runoff election with incumbent Rahm Emanuel. Backed by the SEIU, teachers unions – and Bernie Sanders himself, Garcia's challenge caused Emanuel to tout his progressive bona fides – including raising the minimum wage and investments in pre-K and community colleges.

While Emanuel's victory was representative of the resources that establishment Democrats can muster (including $18 million from wealthy and well-connected donors), it was also symbolic of the restlessness and mobilization of the progressive wing of the party.

It is precisely this kind of grassroots mobilization that Sanders is counting on to win the nomination -- and the presidency.

Photo Source: AP