PORTLAND – This weekend, we mark the third anniversary of the U.S. Supreme Court’s landmark Citizens United decision. And Monday, we celebrate Martin Luther King Jr. Day. There is a powerful message to be had when we link the two. And in truth, the two are quite interconnected.

Dr. King’s lifework was dedicated to ensuring that every citizen had the right to vote and all voices were heard. But if left unchallenged, the effects of the Supreme Court’s decision — and more importantly, the prior court decisions it was based upon — may undermine the integrity and the very foundation of our democracy.

A grass-roots movement has grown in these three years, bringing together many of those who walked with Dr. King in his work — citizen groups, faith communities, students, communities of color — to call for an amendment to the U.S. Constitution that would firmly establish that money is not speech and that human beings, not corporations, are persons entitled to constitutional rights.

In Citizens United, the U.S. Supreme Court built on the “personhood rights” of corporations to expand their “free speech rights” to allow them to spend unlimited amounts of money to influence elections, and spend it in secrecy.

The response was immediate. Outside spending in 2010 broke all records and in the 2012 election cycle was historic. At more than $1 billion, this spending surpassed the total spent by such groups in the four previous election cycles combined.

To understand how we got here, though, we must look not only to the Citizens United decision, where so much attention has been paid, but also back to more than 130 years of court decisions.

For the first 100 years of this nation, corporations were considered artificial entities created by people through charters, granted by states and subject to state and federal laws. Then in 1886, in Santa Clara County v. Southern Pacific Railroad the Supreme Court asserted that the 14th Amendment — which had been ratified to ensure that newly freed African-American men could be considered “persons” with inalienable rights — was expanded to include corporations.

Once corporations became “people,” their lawyers sued to get more “rights” for them. In 1893, corporations were granted due process under the Fifth Amendment; in 1906, they received Fourth Amendment search and seizure protections; in 1922 they were protected under the “takings” clause of the Fifth Amendment, in which a regulatory law is deemed a “taking.”

In 1978, the “corporate person” truly found its voice in First National Bank of Boston v. Bellotti. when the Supreme Court ruled that corporate money equaled “speech” under the First Amendment.

Citizens United simply overturned the state and federal regulations enacted over 30 years to limit this court-granted corporate campaign spending.

Jeffrey Clements, author of “Corporations Are Not People” and a former Portland resident, points out, the problem is not just about campaign finance or free speech. Since the 1970s, corporations have aggressively used this First Amendment right to strike down state and federal laws — from those concerning clean air and fair elections; to environmental protection and energy; to tobacco, alcohol, pharmaceuticals and health care; to consumer protection, lottery and gambling; to race relations and much more.

With this kind of power (and with the current national efforts to marginalize unions and roll back voter rights), the whole concept of “we the people” is in danger of becoming a footnote in our history instead of the foundation of our nation’s existence.

A constitutional amendment is needed to deny corporations personhood and thereby strip corporations of all constitutional rights conferred on them piecemeal by the Supreme Court.

In three years, more than 250,000 people have signed the petition calling for this amendment. Nine state legislatures have passed resolutions demanding it, two states have passed resolutions by citizen initiative, and more than 500 towns and cities have passed the resolution — with two dozen so far in Maine and more in the works.

A constitutional amendment may seem impossible, but all amendments seem impossible until they become reality. Most amendments since the Bill of Rights have expanded democracy or, like the 24th Amendment banning poll taxes, removed obstacles to democracy authorized by the Supreme Court.

The time has come again.

Malory Otteson Shaughnessy of Portland is co-chair of the Greater Portland Move to Amend Group (an affiliate of the national MovetoAmend.org Coalition).