I just got done reading about this a good bit, and I don't believe you can import, but rather, you can sweep the private keys. It is more beneficial to sweep anyway, from what I gather.
There are two forms of the base58, a WIF and a WIF compressed. The WIF has 51 characters and begins with a 5, while the WIF compressed has 52 keys and begins with a K or L. Electrum should recognize both, and I've successfully swept both formats myself.
https://bitcointalk.org/index.php?topic=1841297.0