WASHINGTON — The outcome of Tuesday’s special Senate election in Alabama will set the stage for the 2018 mid-terms no matter who wins: Republican Roy Moore or Democrat Doug Jones.

Here’s the run-down just before the polls open to fill the Senate vacancy created when Republican Jeff Sessions gave up his seat to become Attorney General.

• There is no reliable polling trend that points to a definitive winner.

• The other GOP senator from Alabama, Richard Shelby, told CNN on Sunday he wrote-in the name of another Republican rather than vote for Moore.

• Moore is a vastly flawed candidate. Credible allegations of sexual impropriety with young girls — and his two-time removal from the State Supreme court — have failed to sink his candidacy.

• A win by Moore may fuel 2018 primary challenges to GOP lawmakers in Congress from far-right candidates.

• But Democrats will make Moore a 2018 issue no matter whether he is elected, castigating Republicans for not rejecting outright a man accused of sexually predatory behavior.

This comes in the context of the surging #MeToo movement that materialized in the wake of the Harvey Weinstein revelations. Democrats can do this since Sen. Al Franken, D-Minn., announced his pending departure, and Rep. John Conyers, D-Mich. already quit amid their sexual-misconduct controversies.

• The signs of Moore’s staying power became apparent in September, when he beat the Republican tapped to be the temporary Sessions replacement, Luther Strange.

• Though nationally the primary outcome was cast as a proxy war between President Donald Trump and renegade former Trump White House staffer Steve Bannon, there was actually more at play on the ground.

All politics are local and Strange was tainted and caught up in a controversy that cost the Alabama governor who appointed him his job.

• Though Trump supported Strange — reluctantly — in the final days of this contest the president has become an enthusiastic booster, disregarding the sexual misconduct allegations swirling around Moore.

Democratic candidate for U.S. Senate Doug Jones speaks during a rally on Monday, Dec. 11, 2017, in Birmingham, Alabama. | John Bazemore/AP photo

• Jones is a former federal prosecutor making his first run for elected office. A major resume item is his successful pursuit of the 1963 Birmingham African-American church bombing. As U.S. Attorney, he convicted the two living Ku Klux Klan members who were responsible for the bombing that killed four little girls.

• Jones needs a massive African-American turnout to win. On Monday, former President Barack Obama and former Vice President Joe Biden released robo calls for Jones.

And in the final weekend before voting, former Massachusetts Gov. Deval Patrick and Sen. Cory Booker, D-N.J., stumped in Alabama.

• So how Republican is Alabama? In 2012, GOP presidential nominee Mitt Romney beat Obama by 60.7 percent to Obama’s 38.4 percent.

In 2016, Trump prevailed over Hillary Clinton 62.1 percent to 34.4 percent.

• There are currently 52 Senate Republicans and the number stays the same if Moore is elected.

But . . . if Moore wins, his Senate career could well start with either an ethics investigation or a move to expel him. It takes 67 votes to kick out a senator.