Rick Perry is beginning to learn a hard lesson in the life of a Presidential candidate: they love ya until they stop lovin' ya... and then they love Herman Cain.

Over the past week, Perry's growth on social media --- Facebook in particular --- has come to a surprising, shuttering halt. Since Sept. 23, the day after the Fox News/Google GOP debate, the number of new people "liking" Perry on Facebook has been declining with each successive day. After adding 1,069 new fans on debate day, Perry's growth fell by roughly half each day over the next 3 days. And then things got even worse. 

Perry's downward trend culminated in an actual net loss of 72 fans between Monday and Tuesday, the first time Perry has seen a decline in his social media fanbase.  

This is an unprecedented momentum-sapper for the Texas governor, who jumped in the GOP race on Aug. 13 and quickly amassed a large and active social media following. Perry had been adding an average of 1,007 new fans per day until this week. But since his poorly critiqued debate performance last Thursday, that average dropped by more than half, to just 486 new fans daily.

While Perry's Facebook growth flatlines, underdog Herman Cain surges. Cain picked up 18,814 new fans since Sept. 21 (an average of more than 3,100 fans a day), rising in the sort of hockey-stick graph that campaign managers and Internet venture capitalists love. While the biggest threat to Perry's candidacy remains Mitt Romney, losing ground to other GOP candidates --- whether Cain or the feisty social media force of Ron Paul --- can spell deeper troubles.   

Perry's Facebook momentum is going, going, gone

On Twitter, Perry's week has only been marginally better. While Perry hasn't lost Twitter followers, he is adding them at a slower rate than before --- and considerably slower than both Romney and Cain.  

According to OhMyGov Media Monitoring, Perry picked up 4,501 new Twitter followers since Sept. 21 across his 3 accounts (@GovernorPerry, @TexasGov, @TeamPerry). During the same period, Cain added more than 10,600 followers across his two accounts and Romney more than 14,100 on his sole account. Perry still has the 3rd largest Twitter presence among the GOP candidates, behind Newt Gingrich and Ron Paul.

The social media struggles of Rick Perry should not be dismissed, as they come directly on the heels of the most recent GOP debate and his poor stunningly poor showing in the Florida straw poll.

Not only that, a new Zogby poll released this week has Perry plunging 19 points over the past two weeks. The Zogby poll, conducted Sept. 23-26 of all likely voters and of likely Republican primary voters, shows Perry sitting a whopping 10 points behind the suddenly ascendant Cain, and ahead of Romney by a single point.

On Twitter, look who's catching up

None of these occurrences spells mortal danger for Perry's campaign, but given his late entry into the race, he faces more pressure to amass the kind of momentum that major Republican funders look for, and the grassroots voter support that he'll need to wage a successful campaign in battleground states. The tepid social media growth of late may be an early warning sign --- Perry supporters would be wise to keep a close eye on his social media performance in coming weeks.