Call me cynical but I'm sure some politicians, parties and others favour e-voting precisely because of the scope it gives to rig the vote.
Such rigging doesn't need to be large nor on a huge scale and is consequently very hard to identify and detect, even if it otherwise worked perfectly. It's very easy to tip a marginal to one side and do that dynamically as the vote progresses, even giving the opponents some votes back if it starts to look too suspicious. A marginal swinging one way or another; who'd suspect that ? Swing enough marginals and you get the result you want, tilt the others and the trend makes the marginals' results less suspicious.
Need some smoke and mirrors ? Rig a ward to go to the other party in such a way it is obviously rigged and leave them to take the blame and flak.
Wilder schemes, more open to fraud - email, SMS, 'red button' voting, are acceptable to politicians because fraud is preferable to being shown they have no popular support nor legitimate mandate. Got to keep the gravy train rolling on. Better to be on it with the opposition in power than have everyone being shown as unwanted, so-called democracy clearly failed.
As belief in our politicians and parliament declines you can expect there to be greater desire to move to e-Voting. All in the name of efficiency or cost but really so the people with power keep themselves in power. The System is more important than individual politicians and far more so than the people. Everything will be done to protect the System.