Pennsylvania Republican U.S. Senate candidate Dave McCormick sharply criticized President Joe Biden for an executive order that grants “parole in place” to about 500,000 illegal immigrants married to U.S. citizens, a move Republicans describe as an “amnesty.”

Critics and supporters alike acknowledge it’s a major move that benefits hundreds of thousands of illegal immigrants, just months before the November election. Not surprisingly, Republican candidates like Dave McCormick are using the announcement to make their case against Democrats in Washington, D.C.

McCormick, who is running against three-term incumbent U.S. Sen. Bob Casey Jr. posted on social media, “Biden has let over 10 million illegal immigrants cross the southern border, and now he’s looking to grant mass amnesty to hundreds of thousands.”

He took a shot at his opponent, quipping that since Casey regularly voted for Biden’s agenda then “we’ll know he’ll be right there with him on this, too.”

Casey didn’t respond to a request for comment from DVJournal or from CNN.

“I haven’t seen the proposal, I’ll wait until I see it,” he told the network.

In a statement announcing the executive order, Vice President Kamala Harris said the spouses should be protected so they can stay with their families and “contribute to our communities while they apply for a green card.”

But opponents point out Biden’s actions are almost certainly illegal and likely unconstitutional. The parole statute Biden is invoking, for example, mandates that parole be granted “only on a case by case basis for urgent humanitarian reasons or significant public benefit.”

U.S. Sen. Marsha Blackburn (R-Tenn.) sent Biden a letter Wednesday arguing the president is violating the Constitution by creating legislation from inside the Oval Office.

“As you well know, the Constitution vests the executive with the power to enforce our immigration laws, not to craft them unilaterally. Specifically, the Constitution states that the President ‘shall take care that the laws be faithfully executed.’ If you move forward with implementing this disastrous proposal that alters the legal status of hundreds of thousands of migrants without congressional approval, you would be flouting congressional authority in direct contravention of the Constitution’s separation of powers,” Blackburn wrote.

Legal scholars split down ideological lines on Biden’s executive order.

America First Legal President Stephen Miller said his pro-border-security organization plans to sue.

Calling the executive order a slap in the face to those who legally immigrate into the U.S., Miller said “illegals will have full access to welfare, entitlements, the voting booth, and chain migration, meaning entire illegal alien extended family networks and be made into full voting citizens.”

But The Center for American Progress hailed Biden’s decision as one that kept families together. President and CEO Patrick Gaspard said it gives greater financial stability to American businesses and families. He added families no longer have to worry about figuring out a “broken and outdated immigration system.”

The executive order will keep the nation’s border crisis at the center of the Casey-McCormick race. Polls show immigration is a top issues on the minds of Pennsylvanians. The Commonwealth Foundation found it ranked second on the list of important problems for the U.S. The most recent Marist and New York Times/Siena polls ranked it third.

Casey and McCormick are locked in a close race. RealClearPollings gives Casey an average lead of five points over McCormick. In the presidential race, Republican Donald Trump leads Democrat incumbent President Joe Biden by an average of 2.3 points, according to RCP’s roundup of Pennsylvania polls.

It’s Trump’s lead in the polls that has Pennsylvania Republicans optimistic about McCormick’s chances.

Pennsylvania Republican National Committeeman Andy Reilly told the DVJournal podcast McCormick is one of “the brightest stars” in national and Pennsylvania politics.

“If you meet him, you’re meeting an independent guy,” said Reilly. “You’re meeting someone who is genuine, decent, honest…someone with real experience…I believe he’ll run ahead of President Trump in the southeast, much like Pat Toomey did in 2016.”