An independent Super PAC aligned with Senate Majority Leader Mitch McConnell (R-Ky.) on Thursday voiced strong opposition to Roy Moore's decision to run for Alabama Senate again, saying that nominating him would be "gift wrapping" the seat to Democrats.

"We believe most Alabama Republicans realize that nominating Roy Moore would be gift wrapping this Senate seat for Chuck Schumer," Senate Leadership Fund Communications Director Jack Pandol said in a statement. "It remains to be seen whether Moore can escape his baggage without his candidacy collapsing under its own weight, regardless of what groups on the outside do."

The statement came just moments after Moore, a former Alabama Supreme Court justice, announced that he would challenge Sen. Doug Jones (D-Ala.) for his seat in 2020. The move comes after the controversial Republican lost to Jones in a 2017 special election to replace former Sen. Jeff Sessions (R-Ala.)

Moore gained massive scrutiny during the race over allegations that he pursued sexual and romantic relationships with teenage girls in the 1970s when he was in his 30s. Moore has adamantly denied the accusations, and received support from President Trump during the campaign.

"I will run for the U.S. Senate in 2020," Moore told supporters in Montgomery, Ala. on Thursday. "Can I win? Yes, I can win."

McConnell suggested before Moore's announcement that Republicans would proactively work to oppose his nomination.

"He can do what he wants to, but we're certainly going to oppose him in every way," McConnell told the Associated Press.

Donald Trump Jr., the president's son, came out strongly against Moore's campaign.

"I can assure everyone that by running, Roy Moore is going against my father and he's doing a disservice to all conservatives across the country in the process," he said on Twitter.

Moore's loss to Jones in 2017 gave Democrats their first Senate seat in Alabama in 25 years.

The former judge is among three Republicans - former Auburn University football coach Tommy Tuberville, Rep. Bradley Byrne (R-Ala.) and state Rep. Arnold Mooney - to announce candidacies for the 2020 Republican nomination in Alabama.