Washington (CNN)Republicans across the nation's capital are wringing their hands over the prospect: A special election in deep red Alabama somehow ends up flipping a Senate seat blue.
How a 51-49 Senate could change everything
And the stakes are high. More than a dozen votes in the US Senate so far this year would have failed or been in jeopardy with one fewer Republican member in the chamber, according to a new CNN analysis.
Roy Moore is facing multiple accusations of sexual relationships with teenage girls while he was in his 30s and has denied the allegations. But dozens of Republicans have now called for him to exit the race, raising the prospect of a last-ditch write-in campaign or even his expulsion from the Senate if he's elected to the post.
But, at least for now, Moore has remained steadfast on remaining in the race — raising the possibility of Democratic candidate Doug Jones winning in a major upset and tipping the scales of the US Senate in a dramatic way.
This analysis uses the number of votes that would have needed to flip the other way to change the outcome of the vote, depending on whether the vote required a simple majority or supermajority and assuming Vice President Mike Pence would vote with most Republicans in the case of an even split.
Close votes are common: In fact, a majority of votes taken in this year's Senate so far would have had the opposite outcome if 10 or fewer votes in the chamber had flipped. A third of the votes would have had the opposite outcome if five or fewer votes had gone the other way.
And one in every 20 votes so far this year would have had a different outcome if just one vote had flipped to the opposite side. Here's a look at the votes that wouldn't have passed if just one more Democrat — perhaps Doug Jones of Alabama — had been seated in the chamber.
Say goodbye to Secretary of Education Betsy DeVos: In a Senate divided 51-49 between the two parties instead of 52-48, the two "no" votes from Sens. Susan Collins and Lisa Murkowski would have been enough to tank DeVos's nomination in February. Pence would have never been called in to break the tie.
A procedural vote in July that brought Republicans to the cusp of passing legislation to repeal and replace Obamacare — and set the stage for Arizona Republican Sen. John McCain's dramatic late-night "no" vote that ultimately tanked the bill — would have failed too, by a slim 49-51 margin.
A bill that allowed states to withhold federal dollars from organizations like Planned Parenthood also would have failed — on a procedural vote and the final passage.
A Senate split along party lines 51-49 would have also failed to kill a rule making it easier for Americans to sue banks and credit card companies last month. And senators would have failed to nullify four other rules — two from the Department of Labor, one from the Department of Education and one from the Department of Defense — all of which required just one vote to flip in order to reject it outright.
Still, many votes in the Senate have passed by wide margins. A third of votes in the Senate would have required at least 18 votes to flip in order to fail and a quarter would have required at least 32 votes to flip in order to fail.
Meanwhile, Pence would have likely been called in to break more ties on other votes that just barely squeaked by.
Most important, a critical vote on the budget that laid the groundwork for using a 51-vote threshold for tax reform passed by just a slim 51-49 margin, meaning one more Democrat in the chamber likely would have required Pence's tie-breaking vote for the resolution to pass. Sen. Rand Paul voted no.
The nomination of Mick Mulvaney to be director of the Office of Management and Budget also would have ended up in a 50-50 tie, requiring Pence to push him across the finish line.
Two other nominees — William Wehrum for assistant administrator of the Environmental Protection Agency and Marvin Kaplan for the National Labor Relations Board -- would have needed a tie-breaking vote from Pence, as would a procedural vote on the nomination of Noel Francisco to become Solicitor General.
A Senate divided 51-49 also would have required a tie-breaking vote from Pence to nix government rules on internet privacy and maintaining injury and illness records.
On other votes, it's impossible to know. For example, votes to approve Steven Gill Bradbury as the top lawyer for the Department of Transportation succeeded, but if all the Democrats had showed up to the vote in a 51-49 Senate, his nomination would have failed.