Post-Convention, Romney crosses one million mark on Twitter

(CNN) -- Three days after accepting his party's nomination for president, Mitt Romney on Sunday crossed the one-million mark in Twitter followers.

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"1 million active followers - thanks everyone for your support. Help us keep the momentum going," he said, adding a link to a donation website for his campaign.

Saturday night, he fell just 3,000 followers short of threshold, and around 2 p.m. ET on Sunday, Romney posted that he now had 1 million.

President Barack Obama, meanwhile, is well ahead of Romney, coming in with more than 19.2 million followers as of Sunday afternoon. The White House has made an aggressive push to appeal to Twitter users. The president occasionally tweets from the account himself, and he has taken parts in Twitter town halls in the last year.

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In his tweet, Romney made sure to point out that his followers were "active," after some high-profile figures, including the GOP presidential nominee, have been accused of beefing up their follower list with fake names purchased from "follower agencies." Romney's campaign, however, has denied buying inauthentic names.

Last year, Newt Gingrich especially faced questions over his Twitter account. In August 2011, the former House speaker had 1.3 million Twitter followers, while none his fellow GOP presidential opponents came close to 80,000, including Romney.

A New York based search analytics company PeekYou, said their algorithm results showed only eight percent of the candidate's followers were "humans" and claimed his real follower count was closer to 106,000. The firm excludes businesses and brand accounts as "real people."

Gingrich's campaign maintained the account has higher numbers because Twitter added him to its "Suggested User List." The feature recommends certain names as a way to get new Twitter users started in compiling their favorite people on the microblogging site.

-- CNN National Political Correspondent Jim Acosta and CNN's Ashley Killough contributed to this report.