Given that Electrum is written in Python, and the dependencies of the version in Jessie backports are compatible with the version of Python available in Wheezy, it should be possible to do what you're suggesting. As `root`,
echo deb jessie-backports main > /etc/apt/sources.list.d/jessie-backports.list
apt-get update
apt-get -t jessie-backports electrum
This will pull in `electrum` and `python-electrum` from Jessie backports, but won't affect the rest of your packages. Some of the suggested dependencies ( _e.g._ `python-btchip`) aren't available even in Jessie backports, so some features may be missing.