Conservatives revolt after Trump-appointed Barrett joins liberals in 'shockingly wrong' mail ballot ruling

Barrett was quickly criticized by conservative commentators and politicians.

Jason Snead, executive director of Honest Elections Project, said in a statement that the ruling is "deeply disappointing and misses the mark."

"Federal law is clear: all ballots must be received by Election Day to be counted," Snead wrote. "The Court missed a major opportunity to reinforce election integrity and instead sides with California-style chaos. As Justice Alito makes clear in his dissent, watching ballots trickle in after Election Day and flip races does nothing but damage public trust in our system of government."

Hans von Spakovsky, a former Federal Election Commissioner and Senior Legal Fellow in AAF's Edwin Meese III Institute for the Rule of Law, said in a statement that the ruling is a "grave disappointment."

"As Justice Samuel Alito says in his dissent, joined by three other justices, not only is Justice Amy Comey Barrett's opinion inconsistent with the plain text of those laws and historical practice and precedents, it 'risks further undermining Americans' confidence in election integrity,'" von Spakovsky wrote.

"There is no excuse for a politician, or otherwise, to be against the above three requirements," Trump wrote. "There is only one reason to oppose - CHEATING!"

Trump added, "The House of Representatives has approved this vital Act, THREE TIMES. The United States Senate seems unable to do so. In a time when there is a powerful Communist Movement taking place in our Country, one more dangerous than World War I, World War II, Pearl Harbor, or September 11th, all Dumocrats, and our five Republican Senate Hold Outs, Lisa Murkowski, Susan Collins, Thom Tillis, Bill Cassidy, and Mitch McConnell must vote to SAVE OUR COUNTRY. There can be no more excuses!"

Fox News Digital's Robert Schmad and Anders Hagstrom contributed to this report.