Broadway has a reputation for clannishness, but a look at the last several years of Tony Award nominations paints a slightly different picture, at least as far as musicals are concerned. For the last seven years, the award for best original score (which includes lyrics) has gone to Broadway neophytes. Stephen Schwartz, Andrew Lloyd Webber, the Kander-Ebb tandem, and Marvin Hamlisch are among the veterans who have come up short during that time.

This year’s nominations, which will be announced tomorrow morning at 8:30, could take this tyro-mania to a new level. First-timers Lin-Manuel Miranda (“In the Heights”), John Bucchino (“A Catered Affair”), and Stew and his composing partner Heidi Rodewald (“Passing Strange”) are all but guaranteed spots, and with the two more credentialed entries (“Young Frankenstein” and “The Little Mermaid”) generating little critical buzz, it’s entirely possible that the “Cry-Baby” duo of David Javerbaum and Adam Schlesinger might round out the category — resulting in a sweep for the newcomers. (This would have been practically a given had the Tony nominating committee not determined that the score to “Xanadu” was based primarily on the movie soundtrack and therefore ineligible.)

Several major categories are all but sewn up this year: A handful of plays — “Rock ‘n’ Roll,” “November,” “The 39 Steps,” “The Seafarer” — are fighting for the honor of losing Best Play to Tracy Letts’s “August: Osage County.” Despite late threats from the likes of Laurence Fishburne and Morgan Freeman, Patrick Stewart’s ghoulish take on Macbeth is expected to yield awards both for the production and for himself. And the heavy praise for “Gypsy” made it a presumptive favorite for Best Revival of a Musical — until the following week, when “South Pacific” opened and did its own presuming.

In fact, Bartlett Sher’s mounting of the Rodgers and Hammerstein classic will likely garner more nominations than any other show this year, although “August: Osage County,” “In the Heights,” and “Young Frankenstein” should also get their share. As for the all-important Best Musical slate (which comes with a high-profile production number on national television), can “Frankenstein” or “The Little Mermaid” muscle their way in among the smaller shows? “A Catered Affair” and “Xanadu” are both vulnerable, especially seeing as “Xanadu” opened 10 months ago.

The acting categories are considerably denser. You could practically fill one of the men’s supporting categories with “The Seafarer” and do the same for the women with “Top Girls” — and you still haven’t touched the marvelous ensemble work on “August: Osage County.” As so often happens in high-quality ensemble work, the overall level is so impressive that individual strengths are overlooked. Nonetheless, the potent mother-daughter combo of “August” — Deanna Dunagan and Amy Morton — are both sure things, and the playwright’s late father, Dennis Letts, who transferred with the rest of the Chicago cast soon after being diagnosed with lung cancer, will likely get a posthumous (and deserved) nod.

Jim Norton’s blind drunkard was honored when “The Seafarer” debuted in London and will likely get the same treatment here, even though Ciarán Hinds was just as strong and Conleth Hill even stronger in supporting roles. And maybe, just maybe, Elizabeth Marvel, who has been consistently terrific in plays both big and small for more than 10 years, may finally get recognized for her leading performance in “Top Girls.” (Don’t rule out Martha Plimpton and Marisa Tomei in the supporting category, either.)

Patti LuPone and Kelli O’Hara are both locks for their leading roles in “Gypsy” and “South Pacific,” and Faith Prince’s deglamorized mom in “A Catered Affair” will also be nominated; a group of newcomers will battle for the remaining two spots, including Sutton Foster, Kerry Butler, and Jenna Russell.

As for personal preferences, it would be a shame if the nominators didn’t make room for Eve Best (“The Homecoming”), Brooks Ashmanskas (“The Ritz”), S. Epatha Merkerson (“Come Back, Little Sheba”), Andrea Martin (“Young Frankenstein”), Daniel Breaker (“Passing Strange”), and Sinead Cusack (“Rock ‘n’ Roll”); Peter McKintosh’s costumes and Kevin Adams’s lighting, both for “The 39 Steps”; Rob Ashford’s effervescent “Cry-Baby” choreography, and the pioneering animated projections for “Sunday in the Park With George.”

And if the old guard is concerned by all those whippersnapper songwriters, they can take some comfort in the fact that likely nominees James Earl Jones (“Cat on a Hot Tin Roof”) and Arthur Laurents (“Gypsy” director) first reached Broadway in 1958 and 1945, respectively.