(CNN) If you thought Roy Moore's political future couldn't get any more bleak after four women went on the record with The Washington Post alleging that the Alabama Republican Senate nominee sought relationships with them when they were between 14 and 18, today showed things could get worse for Moore. Much, much worse.

In an appearance Monday afternoon with celebrity attorney Gloria Allred by her side, a woman named Beverly Young Nelson accused Moore of sexually assaulting her when she was a teenager.

"Mr. Moore attacked me when I was a child," Nelson said, recounting that Moore was a regular customer at a restaurant where she worked as a waitress when she was 15 and 16. She described a harrowing chain of events that ended with Moore attempting to force her into a sex act in a parked car -- an episode that, she said, left her with severe bruising on her neck.

Perhaps the most devastating moment of the press conference, however, was when Nelson produced her 1977 high school yearbook that including this inscription : "To a sweeter more beautiful girl I could not say 'Merry Christmas' Christmas 1977 Roy Moore, D.A. 12-22-77 Olde Hickory"

Through a spokesman, Moore dismissed the allegation.

"Gloria Allred is a sensationalist leading a witch hunt, and she is only around to create a spectacle," Moore campaign chairman Bill Armistead said.

But it's hard to dismiss the damage done here.

What Nelson is alleging is sexual assault, not sexual misconduct. One of the four women in the Post story was 14 at the time she encountered Moore, which is below the official age of consent -- 16 -- in Alabama. The others were between 16 and 18 and said the encounters were consensual. Moore was in his early 30s at the time.

Moore's defense to this point has been that the women quoted in the Post story were somehow cajoled into lying about their encounters with him -- fake news and all that.

That defense completely overlooked the fact that all four women allowed the Post to print their names. None of the four women knew one another. None of them reached out to the Post in hopes of having their story told. The Post spoke to more than two dozen witnesses who knew Moore between 1977 and 1982 -- when these instances allegedly took place -- and corroborated the facts as the women relayed them.

Now, Nelson adds her name to that list. Like Leigh Corfman, who alleged that Moore touched her -- and urged her to touch him -- when she was 14, Nelson said she voted for Donald Trump in the 2016 election. Which makes it difficult to cast this as some sort of politically motivated gambit.

To believe Moore's denials at this point, you must also believe that:

1. All five of these women, who say they have never met one another, are not only all lying but doing so in a coordinated manner with remarkably similar stories of Moore's pursuit of them.

2. The dozens of corroborating witnesses that the Post spoke to are also part of a broad -- and very well-organized -- conspiracy to keep Moore from the Senate.

3. Nelson forged -- or had someone forge -- an inscription on her 1977 high school yearbook from Moore, OR Moore signing a teenage girl's high school yearbook -- and noting she was "beautiful" -- was entirely innocuous.

Are there people in Alabama -- and nationally -- that believe all of those things? Sure. But it appears that Republican Senate leaders are not among them.

Senate Majority Leader Mitch McConnell told reporters in Kentucky Monday morning that the time had come for Moore to "step aside." Then, even as Nelson's press conference was wrapping up, Colorado Sen. Cory Gardner, who heads the party's campaign committee, released a statement calling on Moore to be expelled from the Senate if he manages to win the special election on December 12.

"If (Moore) refuses to withdraw and wins, the Senate should vote to expel him, because he does not meet the ethical and moral requirements of the United States Senate," Gardner said.

President Trump, who continues to travel in Asia, has not said much of anything on Moore's situation -- insisting that he has been too busy to focus on the allegations. But Trump returns to Washington on Wednesday and may be pressured to say something even sooner than that by way of clarifying where his White House comes down on Moore

Regardless of what Trump says, however, it's hard to see how Moore ever actually holds a Senate seat. Gardner's pledge to vote to expel him if he wins means that such a motion would almost certainly pass. What senator -- Democrat or Republican -- could or would vote against expelling Moore at this point?

If past is prologue, Moore will continue in the race -- arguing that this is all just one big conspiracy by, well, everyone, to get him. But, it seems clear now that no matter what Moore does, his chances of becoming a senator are increasingly minuscule.