In pointing out that Mormon marriages are eternal once sealed in a Temple, I implied this made divorce "really not that much of an option". The truth is: the eternal celestial marriages do make divorce far more stigmatized among Mormons and doubtless contribute to their relatively low divorce rate. But Mormons can be unsealed in the Temple just as they are sealed. This LDS site explains:
Although being sealed in the temple means being together for time and all eternity we live in a day and age when divorce is prevalent. People marry, divorce, and remarry. In doing so many people who divorce no longer desire to be with their ex spouse for all eternity. Most who remarry desire to be with their new spouse in the next life instead of their previous spouse, to whom they are still sealed.
Imagine living with an embittered ex-spouse for eternity! But the Mormons, like Romney, are nothing if not flexible. Notice the "we live in a day and age when divorce is prevalent" excuse: you won't get that kind of concession to the times from, say, the Pope. But this is more complicated than it might sound:
For a woman (called a sister) to receive a temple divorce she must be ready to be sealed to another man and the two of them must both be temple worthy and hold a current temple recommend.
Because a man can be sealed to more than one woman he does not need to have his temple sealing canceled to be able to be sealed to another woman, and a request to do so would most likely be refused unless his previous wife is ready to be sealed to another man and requests to have her temple sealing canceled. What a man does need, though, is permission to be sealed to another woman. This process is done through the bishop and must also be approved by the First Presidency.
My italics. Notice the patriarchal dynamic here. Women are to be kept married as far as is possible. Men not so much. And notice too that a husband, if his wife died, could re-marry in a Temple, and have two eternal wives in the afterlife. Which should make the afterlife lively – and perhaps a little awkward at times.