Wikipedia has put a silver padlock icon on the top right hand side of their entries.
This means that anonymous users cannot make editorial changes to content relating to the politicians.
The measures were taken after comedian Stephen Colbert suggested on US TV that viewers should edit the pages.
Mr Colbert was following up on earlier media reports suggesting that the popularity of election candidates could be determined by the number of edits their entries on Wikipedia had received, volunteer media coordinator David Gerard told BBC News.
As a result, more people started to tinker with the politicians' pages.
They now have a partial lock, meaning that anonymous users and those without a Wikipedia account are currently unable to make changes to the pages of Mr Romney, Senators Rob Portman and Marco Rubio, Governor Chris Christie and others.
"It's supposed to be an encyclopedia so a bit of amusement is fine but too much gets messy really," said Mr Gerard.
"We try to keep stuff as open as possible, so once it calms down they'll probably be open again."
It is particularly important that entries about living people are editorially sound, Mr Gerard said.
Not many pages are completely locked down.
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