Your backup should be a wallet.dat file, which would include your default. For a paper or text backup of the default, you can probably use the help/debug console commands - dumpprivkey looks promising. You wouldn't be importing into a new wallet.dat file, you'd be copying.
If you import an address, it still sends from the wallet address. Imported addresses are only "receiving" addresses.
The model is "many receiving addresses, a single send address" because you can trust send addresses to be updated / maintained / owned / refreshed by an active voter account. Longer term history at receiving / imported addresses would mostly mean commerce / payment / business activity. The imported receiving addresses would form your "reputation" backbone on the network...your economic history. The wallet addresses form your "voter identity" backbone behind them...your political history. Your "voter identity" is linked to a "personal identity" at any given website by voluntarily disclosing out of network info - a forum screenname, ID docs, a related btc address, etc...but could be maintained completely separate and private out-of-network if desired.
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That said, we could use a "ballot card copy / reset" option though. Right now, the only way to "clear" a vote is to send over 10 Satoshi, then create a new wallet and vote again. That's fine if you're only voting for one address per wallet, but I like to do all my cXo votes from one wallet....So updating one vote means redoing all.
Probably as a .bat or other script that could be launched, close, and restart the gui? Maybe read vote record of current default address, user input for new votes (or clear all), export all keys, create new wallet, import all keys, sweep to new wallet, reset / update votes?