The Streatham MP pulled out today citing excessive scrutiny of his private life, including reporters showing up at the door of his girlfriend's 102-year-old grandmother.
Social media users called it "very sad" and "a damning indictment of our despicable gutter press".
Chuka Umunna's withdrawal is very sad for him and for Labour. Had a lot to offer the future of the party.— Jane Merrick (@janemerrick23) May 15, 2015
Nooo Chuka...you were our only hope :(— ALEX. (@LAMPER_) May 15, 2015
Sad that Chuka has pulled out of the leadership contest because of media attention on his family. Politics must change.— Jayne Bryant (@JBryantWales) May 15, 2015
I feel sorry for Chuka now :(— Polaiteoir (@ashrouen) May 15, 2015
Very sad news about Chuka Umunna. The right wing press are even more partisan and malicious now than they were in the eighties.— rupertgoold (@rupertgoold) May 15, 2015
Chuka Umunna stepping back from the Labour leadership race is a fairly unsurprising, but damning, indictment of our despicable gutter press.— Michael Devereux (@mikeydevereux) May 15, 2015
Dan Jarvis and now Chuka rule themselves out of standing due to not wanting to inflict tidal wave of hate on their families. Sad indictment— martyn notman (@NFGmart) May 15, 2015
Feel sorry for Chuka Umunna. Not my choice but sad indictment of world we live to feel he has to withdraw due to intrusion into private life— Michael (@TheRightArticle) May 15, 2015
I don't have Chuka's politics (at all) But really hope he hasn't been forced to withdraw for anything we shouldn't give a toss about in 2015— Owen Jones (@OwenJones84) May 15, 2015
i hope Chuka's dropped out to concentrate on his UK Garage DJing. it's probably because of racism though, which is sad.— Mike Hemsley (@mikejhemsley) May 15, 2015
Seen couple of tweets from people that might know that seem to me to imply Chuka is gay. Sad if that is the reason.— Happy Hornet (@Eagle2974) May 15, 2015
I like Chuka Umunna. Sad face :(— Claire T (@CTallers) May 15, 2015
@ChukaUmunna ... why on earth did u step aside? :-( I thought we would finally have a leader I was happy to vote on x— Rissa Tweetman ♡ (@RissaHalls) May 15, 2015
Chuka Umunna basically pre-smeared. The internet at its worst :(— Christopher Hooton (@ChristophHooton) May 15, 2015
Chuka Umunna withdraws Labour leader bid - that's a shame. Labour are stuffed now :(— steve harding-hill (@harding_hyphen) May 15, 2015
Sad to hear Chuka Umunna has withdrawn from the Labour contest, but his time will come.— David McArdle (@davemcardle) May 15, 2015
Umunna's team were confident that he would secure the 35 nominations from fellow MPs required to mount a leadership bid, but he decided that it was not the right time for him to press ahead.
He is not at this stage endorsing any other candidate for the leadership.
Umunna, who said he hoped to remain a member of the shadow cabinet, apologised to those who supported his bid and said he had always harboured doubts about whether he was ready to step up to the biggest role.
"I apologise to all those who have kindly supported and encouraged me to do this and for disappointing them. I know this will come as a surprise to many but I had always wondered whether it was all too soon for me to launch this leadership bid - I fear it was.
"Most importantly, I continued to have very real concerns and worry about this bid's impact on those close to me.
"I intend to carry on playing my full role as a proud member of our shadow cabinet taking on the Tories.
"I also hope to play a leading role in Labour's campaign to keep the UK in the EU during the forthcoming referendum, which is absolutely crucial. Most importantly, I will as ever continue to serve the area I know and love - the Streatham parliamentary constituency."