The Audience play set for post-election rewrite
The writer of The Audience, a play about the Queen's private meetings with her prime ministers, is poised to rework the script to reflect the result of the general election.
Peter Morgan told the BBC that he had "a lot of writing to do in the coming days".
The play has returned to London's West End with Dame Kristin Scott Thomas as the Queen.
She said the prospect of a new scene to learn was "a little nerve-wracking".
The original production of The Audience opened in the West End in 2013 with Dame Helen Mirren in the lead role.
Dame Helen is now starring in the Broadway version.
Speaking after Tuesday's opening night performance, Morgan said he had already made "significant changes" for the 2015 version.
These include dropping the character of James Callaghan, and adding Tony Blair.
In another updated scene, the Queen and David Cameron refer to the imminent general election.
"Seeing it as close to an election as we are sharpens people's appetite for prime ministers in disarray and crisis," he said.
"I could be having a sleepless night between Thursday and Friday writing a new scene for [Labour leader Ed] Miliband or Cameron.
"Whatever happens, the next scene the Queen has with a prime minister will either be accepting Cameron's resignation or asking him to form a new government.
"We are in the process of auditioning a few Ed Milibands just in case, because otherwise we'd be left looking like fools."
Dame Kristin said meeting the Queen to receive her damehood at Buckingham Palace in March had been a "bizarre" experience.
"I've always not really wanted to play people who actually existed and I gave in to this one," said the 54-year-old.
"It was odd meeting someone I was going to pretend to be."
She said she had "never really paid attention" to the Queen before taking on her latest role but was "a huge admirer" now.
Here is what the critics have said about the new production of The Audience.
Michael Billington, The Guardian
Scott Thomas gives a highly accomplished performance that veers between mischievous irony and icy hauteur, but without quite convincing us of the Queen's ability to act as a therapeutic counsellor to her disturbed premiers.
Holly Williams, The Independent
Scott Thomas is certainly regal: elegant, refined, chin lifted and nose looked down. This is a rather arch interpretation; the slightest pursing of lips may suggest one is amused, or deeply disapproving. She glides smooth and cool as marble through on-stage costume changes and time-shifts.
Looks-wise, it's not the most natural fit - Scott Thomas is just glamorous in a way even twinsuits over fatsuits for the later years can't hide - but her slicing comic subtlety is a treat.
Dominic Cavendish, Daily Telegraph
Elegant Dame Kristin easily holds her own against the gilded memory of Dame Helen Mirren - now reprising her turn, to Tony Award-nominated effect, on Broadway.
Her Elizabeth is taller than the monarch, and more icily "regal"; the actress implies that the Queen takes a certain enjoyment at the discomfort she can cause with a telling, reproving silence or too-pained diplomatic smile.
The Audience runs at the Apollo in London until 25 July.