There's a blackout in the UK -- on election coverage

London (CNN)There's an eerie sense of calm in Britain this Thursday.

After weeks of bitter name-calling, raucous political debate and media saturation of the UK general election, the airwaves are oddly serene owing to strict rules about what broadcasters can and cannot say on election day.
As millions of voters trudge to polling stations in schools, church halls and even country inns, top television and radio news programs are filled with the aftermath of the Nepal earthquake and the deteriorating security situation in Afghanistan.
Apart from a few camera shots of leaders like Conservative Prime Minister David Cameron and Liberal Democrat Nick Clegg coming out of polling stations after casting their vote, it seems like the frenzied six-week election campaign never happened.
    In the UK, television and radio shows are forbidden from discussing campaign issues, talking about polls or dissecting individual candidates until the polls close at 10 p.m. (5 p.m. ET). However, the regulations are subject to all sorts of apparent contradictions and loopholes, particularly since newspapers are not under their purview.
    Still, that's much different than in the United States, where candidates frequently campaign on election day itself. They often phone into radio shows or participate in television interviews in swing states late into the day as they try to drive the maximum number of voters to the polls.
    Any attempt to impose UK-style restrictions in America would not only be furiously rejected by broadcast news outlets, they would almost certainly fall afoul of the U.S. Constitution's guarantee of free speech.
    The British rules are enforced by the Office of Communications (Ofcom), which regulates TV and radio broadcasters. They are designed to ensure impartiality of political coverage and to prevent broadcasters from swaying public opinion as Brits go to cast their votes.
    The rules are part of a wider package of regulations meant to ensure that individual candidates and parties get a fair share of broadcast coverage throughout the election campaign.
    In practice, the regulations mean that any content that could be reasonably seen by a viewer or web surfer in the UK should avoid direct discussion of candidates or issues or poll numbers. Existing content does not have to be taken down, but broadcasters must be careful not to infringe on the rules by posting fresh web content.
    Broadcasters have to make do with rather bland coverage during the time that polls are open. Companies with websites seen in the UK and elsewhere in the world -- including CNN International -- also have to figure out how to avoid breaking the rules.
    Journalists cannot discuss the strengths and weaknesses of a particular candidate on polling day and, unlike in the United States, are prohibited from interviewing voters at polling places and asking them how they voted. That would be seen as an attempt to shape the outcome of the election.
    The ban on discussing polls includes exit polls, and editors face stiff fines and even imprisonment if they publish such material while polls are open.
    But there are gaps in the prohibitions. Although the regulations do not cover social media, reporters based in the UK still have to be careful. Tweets, for example, could be problematic if they are embedded in a broadcast outlet's website.
    The rules do not prohibit foreign correspondents based in Britain from talking openly about the election -- as long as their output could not reasonably be seen by a British viewer.
    And a curious voter who can't bear to go a day without polling or comment still has plenty of options.
    Since the Ofcom rules do not apply to newspapers, with just a few clicks, voters can get lots of prohibited broadcast content -- last-minute polls, outspoken commentary and articles savaging the top candidates and parties -- on newspaper websites.
    Thursday's dead tree newspapers also plastered all kinds of election content and ideological appeals to voters on their pages.
    In fact, there's something of a UK tradition of lurid front-page election splashes. In one of the most notorious examples, the Sun tabloid in 1992 produced a front page featuring the face of then-Labour Party leader Neil Kinnock in the shape of a light bulb.
    "If Kinnock wins today, will the last person to leave Britain please turn out the lights," the headline read.
    The stiff rules don't mean election day fun and debate is banned altogether: A social media meme quickly gathered pace on Thursday as media personalities and others argued on Twitter about whether they could take their dogs into polling stations.
    But the long arm of the election rules intruded even into this distraction. A BBC Twitter account pictured a dog outside one polling station, but blacked out a badge it was wearing in support of one of the political parties.