The GOP is now the party of white supremacists and billionaire donors. It's the party of gerrymandering, false accusations of election fraud, and voter suppression. It's the party of Donald Trump. The GOP has made it clear that any Republican in favor of fair elections will be ousted, ostracized, and threatened with physical harm or death. There's no room for Romney, Cheney, or Jeff Flake in the new Republican party. It's doing everything it can to establish minority rule in the United States, including calling for rioters to attack elected officials. Republicans will never certify a Democratic win again because if they do, they'll be admitting they lost fairly and that most voters don't support them.
In an essay for Washington Monthly, David Atkins asks, "What Happens When Republicans Simply Refuse to Certify Democratic Wins?"
The short answer is that the matter would go to the courts. The clear rule of law says that state legislatures cannot overrule the will of the voters. But if the vote isn't officially certified, there is no official will of the voters. There are laws stating that elections must be certified by certain dates, but there a dearth of precedent around what happens if they don't. And given the Trump administration's stacking of the lower courts and the wildly conservative imbalance on the Supreme Court, it's not clear that the outcome would favor the preservation of democracy. Nor is it clear that the matter would be resolved in time to prevent civil conflict–or, in fact, that Republicans in the state or federal legislative branches would honor the Court's authority should it side against them.
A Republican Party hostile to democracy can use America's creaky Constitutional system to create a series of unprecedented roadblocks to majority rule. Not just by suppressing the vote or drawing unfair districts, but by refusing to accept the vote itself. The result could throw the nation into political violence unseen since the days of Ku Klux Klan terrorism if not the Civil War itself.