The U.S. Supreme Court has been hearing arguments about President Barack Obama's immigration executive actions on Monday, April 18, a development that could have major consequences on the 2016 presidential race for the White House.

Before the court is the burning question of if the president was within his legal authority in 2014 when he moved to unilaterally act to protect approximately 4.9 million undocumented immigrants from the further threat of deportation.

Legal Ruling one of Biggest of Obama Administration 

The high court's decision stands to easily rank as one of the most consequential legal rulings of Obama's two-terms in office and shapes up to carry plenty of weight in the minds of voters set to decide the critical issue of who should reign as his successor over the next several months.

Republican front-runners Donald Trump and Ted Cruz have openly taken on hard-line stances against immigration reform, with both pledging to mass deport up to 11 million immigrants should either of them be elected. In addition, Trump has vowed to build a massive wall along the Mexican border to further keep out immigrants.

In contrast, Democratic candidates Hillary Clinton and Bernie Sanders have both pledged allegiance to a plan of immigration reform.

Support on Issue Breaks Down Along Partisan Lines

Supporters on both sides of the issue are expected to line the streets of Washington on Monday, making certain that their voices are heard on an issue that has largely splintered along partisan lines.

The president was moved to action after House Republicans repeatedly resisted his calls for bipartisan legislation and shot down a Senate proposal that would have provided immigrants with a path toward citizenship. Soon after the president enacted his own legislation, the state of Texas and 25 other GOP led states moved to file suit.

Known as Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA), Obama's plan stood to allow the estimated four million people that have lived in the U.S. without authorization since 2010 the chance to enter a program that shielded them from deportation and supplied them with work permits.

To qualify for the program, one would have to have no criminal history and record children who are U.S. citizens or lawful permanent residents.

The plan never saw the light of day after it was blocked by a federal judge in Texas. The New Orleans-based 5th U.S. Circuit Court of Appeals upheld that decision in November and the Supreme Court is expected to formally render its decision by the end of June.

With the high court now evenly divided with four liberal justices and four conservatives following the February death of conservative Antonin Scalia, no one knows how the proceedings might turn out.

What's clear is that Republicans are doing all they can to stop all proposed legislation in its track. The GOP led House formally petitioned the court to be heard on the issue and has been granted time during the oral arguments phase of the proceedings to argue against the President's actions.

"The best way" to solve this problem is with "a common-sense" immigration reform bill like the one passed by the Senate," the president previously argued in a speech he delivered before the nation. "But until that happens, there are actions I have the legal authority to take as president."