the phrase 'steal an election'?

it means, literally, to take something that belongs to another.  I don't see the issue.Not really stealing the election, but stealing the win of that election, if that is the detail you need.

It is an idiom, suggests a subjective opinion that a ballot result should have gone to the complainer but didn't. Occurs a lot in sport - We was robbed, meaning we lost but should have won. It seems to be a baseless allegation when there was no evidence produced of wrongdoing.

Something doesn't have to have material existence for you to steal it. You can steal an idea, or someone's love, or an election.

It’s not an idiom.  “Steal” has the identical meaning that you have mentioned.

This picture explains it nicely.

It is rhetoric and hyperbole. Just like "stolen supreme court seat". Phrases designed to create drama among partisans.

Trump and his supporters made it up, with absolutely no evidence of widespread voter fraud. But no, they intended "steal" in it's usual meaning, to take something away from someone. 

Simple and Concise.

The CHEATING aspect does not have the same power. Cheating is now normal, stealing (the word) still has a sting.
It really is not considered "Voter Fraud" when whole new ballots are injected into the system. (Once in the system, recounts don't work.)
Dead voting, moved away voting, invalid registered voters voting,  That IS Cheating, not stealing.
Bringing in boxes of extra Ballots, now that is stealing.

https://www.youtube.com/watch?v=WUEqh07E4dY&t=14s

Be happy forget about it.  The Government in power protects you. You don't even need to vote, they will do it for you in the future.
Remember the NRA, and the MAGA people are all TERRORISTS who will soon be disarmed and Reeducated to be proper citizens.
Already plans are working to seize their Children for Deprogramming Camps in the Summer.

No.............