Gathering in Washington called attempt to inject humour and tone down partisan division.
Barack Obama, the US president, was planning to attend three rallies on Saturday to support candidates from his Democratic Party, but one gathering he would not due to attend was held in Washington DC.
Thousands of people gathered in the US capital to watch two popular political satirists appeal for moderation and civility in polarised times, in the run-up to the congressional elections on November 2.
The alternative rally had generated extensive buzz on the internet, with more than 226,000 people on a Facebook page created for the event saying they would attend.
Organisers insisted the idea behind the Rally to Restore Sanity and/or Fear hosted by Jon Stewart of Comedy Central's Daily Show and Stephen Colbert of The Colbert Show was not about politics.
Stewart and Colbert encouraged attendees to bring signs with slogans such as "Real patriots can handle a difference in opinion", "It could be worse but let's not make it that way", and "Death to Nobody".
Stewart said the day was about toning down anger and partisan division.
Al Jazeera's Nick Spicer reports from the rally.