The election of Donald Trump will likely define the 2010s -- but a single day in January 2010 set his rise into motion

On Jan. 21, 2010, then-Supreme Court Justice Anthony Kennedy cast the deciding vote in the Citizens United case, which was brought by a group chaired by David Bossie, who would later serve as Trump’s deputy campaign manager.

Kennedy wrote in the majority decision that limits on independent expenditures violated the First Amendment rights of corporations and other groups, effectively overturning spending restrictions dating back more than a century.

The decision allowed corporations to spend unlimited money on campaign ads as long as they did not formally coordinate with candidates or political parties. According to Kennedy, there could not be corruption, because “an independent expenditure is political speech presented to the electorate that is not coordinated with a candidate.”

Some have argued that the ruling was the “logical next step” after the court’s 1976 Buckley v. Valeo decision, which said election spending limits may violate the First Amendment. But the Supreme Court ruled in favor of corporate limits in 1990 and then upheld limits on corporate and union spending in 2003.

The Citizens United ruling was later compounded by Republican efforts to block transparency rules, Federal Election Commission rulings and further court decisions like McCutcheon v. FEC, paving the way for the creation of super PACs, or committees which can spend unlimited sums of money to promote or oppose candidates while hiding the identities of their donors.

The impact of the Citizens United ruling and subsequent campaign finance changes are undeniable. In 2010, the biggest Republican donor of the election cycle spent $7.6 million to support conservative candidates, according to the Center for Responsive Politics (CPR). Just eight years later, casino mogul Sheldon Adelson and his wife, Miriam, donated $122 million to support GOP candidates, or more than 15 times as much.

Democrats pumped big money into elections, too. Presidential contender Mike Bloomberg spent $95 million during the last election cycle, while fellow billionaire candidate Tom Steyer spent more than $73 million, according to CPR data.

There was certainly loads of money pumped into elections prior to Citizens United. The 2008 presidential election, which was the last national contest before the Supreme Court decision, saw about $338 million in outside spending. But the amount of outside cash injected into the presidential race skyrocketed to more than $1 billion in 2012 and $1.4 billion in 2016.

Such massive expenditures are not limited to presidential races. The 2018 midterm election cycle was the first in history to see more than $1 billion in outside spending — up from $69 million just four cycles earlier and $567 million in 2014, according to the CPR.

Super PACs quickly became the biggest outside spenders. In 2018, the House Republican-linked Congressional Leadership Fund spent $136 million, the Senate Democratic-aligned Senate Majority PAC spent $112 million and the Mitch McConnell-connected Senate Leadership Fund spent $94 million, according to the CPR.

Though both parties have raised and spent hundreds of millions in outside money — and the Citizens United ruling has been criticized by both former President Barack Obama and Trump — researchers at the University of Chicago, Columbia University and the London School of Economics and Political Science found that the rise of dark money has resulted in a huge advantage for Republicans in state legislature races, particularly in “states with weak unions.”

“We find that Citizens United increased the GOP’s average seat share in the state legislature by five percentage points. That is a large effect — large enough that, were it applied to the past twelve Congresses, partisan control of the House would have switched eight times,” the researchers wrote in a Washington Post op-ed. “In line with a previous study, we also find that the vote share of Republican candidates increased three to four points on average.”

The result has been a shift much further to the right in numerous state legislatures and an increase in “ideological extremism,” which was more prevalent among Democrats, according to the study.

In the 2010 election, the first to see a massive upswing in outside money, Republicans captured two dozen state legislative chambers ahead of a game-changing nationwide gerrymandering effort, which made it harder than ever for Democrats to win back the seats they lost.

“Without Citizens United every frontline Congressional race of the last two cycles are TOTALLY different,” Fordham Law Professor Zephyr Teachout tweeted. “A billion in outside spending in 2018. And that is just a tiny fraction of the impact.”

Despite Kennedy’s insistence that there could be no corruption because candidates cannot coordinate with super PACs, the ruling has also led to corruption as candidates flout rules preventing them from coordinating with the PACs.

“The supposed barrier between candidates and unrestricted super PACs is flimsier than ever,” Roll Call reported just four years after the ruling. “As midterm elections approach, complaints are rolling into the FEC from both parties about super PACs that share vendors, fund-raisers and video footage with the politicians they support.”

GOP leaders like Paul Ryan devised ways to solicit money directly from billionaires like Adelson by using go-betweens. The New York Times reported in 2015 that Republican presidential candidate Carly Fiorina had “aggressively” exploited loopholes to allow a super PAC to effectively run her campaign.

And the corruption is not merely limited to exploiting loopholes in the law. Obama warned in a State of the Union speech that the Citizens United ruling could lead to foreign interference in U.S. elections. Supreme Court Justice Samuel Alito could be seen mouthing the words, “Not true.”

But Obama's foreshadowing turned out to be remarkably true. Lev Parnas and Igor Fruman, the two associates of Trump's personal attorney, Rudy Giuliani, were recently indicted on charges that they illegally funneled foreign money to Republican politicians, including a $325,000 contribution to a pro-Trump super PAC.

George Nader, an adviser to Saudi Arabia and the United Arab Emirates who was linked to efforts to aid Trump’s campaign during the election, was also indicted for allegedly funneling $3.5 million into elections, including a $1 million contribution to a Democratic super PAC.

In 2012, a foreign-owned company made a $1 million contribution to a pro-Mitt Romney super PAC.

Democratic presidential candidates, including Sen. Bernie Sanders, I-Vt., have premised their campaigns on driving big money out of politics. Sanders has long called for a constitutional amendment to repeal Citizens United, which was echoed by Sen. Elizabeth Warren, D-Mass., and others at the party's December primary debate.

But it may be nearly impossible to meet the high threshold to ratify a constitutional amendment. There has only been one amendment ratified since 1971. While House Democrats voted to approve H.R. 1, which called for the ruling to be repealed, there appears to be little to no support for the legislation from Republicans in the upper chamber.

Groups like the American Civil Liberties Union have decried these efforts as attempts to “ban political speech.”

“In our view, the answer to that problem is to expand — not limit — the resources available for political advocacy. Thus, the ACLU supports a comprehensive and meaningful system of public financing that would help create a level playing field for every qualified candidate,” the organization said. “We support carefully drawn disclosure rules, we support reasonable limits on campaign contributions and we support stricter enforcement of existing bans on coordination between candidates and super PACs.”

Some local governments have tried to counter the rise of dark money with public financing. Seattle’s “democracy vouchers” give voters $100, which they can donate to any campaign in a local election. Democratic presidential candidate Andrew Yang has proposed a similar “Democracy Dollars” program, which would expand this initiative across the country.

But while cities, states and federal lawmakers grapple with the rise of dark money in politics, one thing that is clear is that Citizens United irrevocably changed politics over the course of the last decade — and beyond.

Kennedy himself admitted in 2015 that the disclosure requirement he believed would fix any potential issues of corruption was “not working the way it should.” FEC Commissioner Ann Ravel quit in 2017 over the state of campaign finance, writing in her resignation letter that “our political campaigns have been awash in unlimited, dark money" since the Citizens United decision.

“Most of the funding comes from a tiny, highly unrepresentative segment of the population,” she wrote. “Disclosure laws need to be strengthened, the broken jurisprudence of Citizens United re-examined, public financing of candidates ought to be expanded to reduce reliance on the wealthy and commissioners who will carry out the mandates of the law should be appointed.”

A Brennan Center report pointed out that a small wealthy group of Americans now wields “more power than at any time since Watergate, while many of the rest seem to be disengaging from politics.”

“This is perhaps the most troubling result of Citizens United: in a time of historic wealth inequality,” report author Daniel Weiner wrote, “the decision has helped reinforce the growing sense that our democracy primarily serves the interests of the wealthy few and that democratic participation for the vast majority of citizens is of relatively little value.”