Four or five?

That’s the question everybody’s asking about the upcoming Tony Award nominations now that the organizers of the theater world’s highest-profile awards ceremony have decided that under certain circumstances, some major production categories, including new musical, may be expanded from four slots to five.

That possibility would be a big deal in any year, especially for the new musical award, which is generally recognized as the only Tony to have a major influence at the box office. The rule change seems especially significant this year — when a crowded pack of new tuners hasn’t yielded a front-runner that has unified the Main Stem in a wave of enthusiasm the way shows like “The Producers” and “The Book of Mormon” have in prior years.

“It’s going to be like the Wild West out there,” says one legiter of the nominations, due to be announced April 29.

In an anything-goes race, the idea that one additional show might gain access to the night’s televised publicity boost has obvious appeal. The new regulation allows for the supersizing of a major production category (new musical, new play, musical revival or play revival) if nine or more titles are eligible for that category. The 2013-14 candidates for new musical easily number a dozen, including “A Gentleman’s Guide to Love and Murder,” “After Midnight,” “The Bridges of Madison County,” “Rocky,” “Aladdin,” “If/Then” and “Bullets Over Broadway.” (There are also more than nine potential contenders for play revival, since Tony organizers have opted to consider plays-in-rep “Twelfth Night”/“Richard III” and “Waiting for Godot”/“No Man’s Land” as two separate productions each.)

Here’s the catch: The upgrade from four to five will happen only if, during the nominating process, a fifth show achieves a vote tally that puts it in the same ballpark as the show with the fourth highest total. So legiters won’t know exactly how many productions will be in the running until the morning of the nominations.

That uncertainty ratchets up a notch when no one can identify one or two clear favorites in the group.

Among a sampling of theater industry types, the only new musical consistently viewed as a shoo-in for a nomination is “A Gentleman’s Guide to Love and Murder,” the musical murder-spree comedy that scored enthusiastic reviews when it opened in the fall. Cotton Club revue “After Midnight,” another critical darling from the autumn, also gets mentioned regularly as a likely suspect for a nom. All the other candidates tend to have just as many points in the con column as in the pro.

Additional questions lie in how the Tony admin committee will decide to classify “Lady Day at Emerson’s Bar and Grill,” the Billie Holiday bio starring Rialto fave Audra McDonald; Neil Patrick Harris topliner “Hedwig and the Angry Inch”; and Sutton Foster vehicle “Violet.” “Lady Day” was billed as a musical when it ran Off Broadway in 1986, but it could feasibly be considered a play with music. In addition, “Lady Day,” “Hedwig” and “Violet” appear on Broadway for the first time, meaning each could qualify as a “new” show unless the nominators deem it a revival of a work that has achieved notable prominence in the canon. (The latter possibility seems likely for all three titles.)

In such a scattershot year, it seems unlikely that one or two productions will own the nominations board the way “Kinky Boots” and “Matilda” did last year, scoring 13 and 12 noms, respectively.

The only real certainty this year? The lead actress in a musical race will be a diva smackdown of epic proportions.

Kelli O’Hara (“The Bridges of Madison County”), Idina Menzel (“If/Then”), Foster (“Violet”) and McDonald are all bona fide musical-theater stars, any one of whom would be the one to beat in any other season. Also in the mix are Michelle Williams in “Cabaret” (opening April 24), impossible to discount due to her awards-season muscle in Hollywood, and Jessie Mueller, who earned universal raves for her perf as Carole King in “Beautiful.” And there’s always a chance that nominators will deem Marin Mazzie a lead for her perf in “Bullets Over Broadway.” It all adds up to seven names, at least, in a category that can accommodate only five.

With other irregularities set to make things interesting — such as the fact that high-profile “Cabaret” repeaters Alan Cumming, Sam Mendes and Rob Marshall probably won’t be eligible for awards because they were nominated for the same production in 1998 — it all boils down to a lot of questions that won’t get answered until April 29.

As one industry vet predicts: “People are going to be biting their nails even more than usual Tuesday morning.”