Double Spend
Answer from Blockchain.info:
The bitcoin mempool is currently backlogged, which is causing a delay with transaction confirmations. You can follow it live on this chart, which shows all pending bitcoin transactions on the bitcoin network – https://blockchain.info/charts/mempool-count. This is impacting the entire bitcoin network, not just Blockchain.info.

An unconfirmed transaction will eventually be accepted into a block by whichever mining pool mines the block, or the transaction will eventually be rejected by the bitcoin network after an estimated one to seven days. If it eventually is rejected, then the funds would remain at the bitcoin address they were sent from. The only thing you can do at this point is to wait and see if the transaction is accepted into a block. Like all wallet providers, Blockchain.info has absolutely no control over this, and cannot expedite transactions. This is always dependent upon the bitcoin network of miners, which we are not a part of.