Someone has made the case that it is. I don't have the original source, but was sent this:
1. Obama is KNOWN evil but he has only 4 more years to go.
2. Romney is KNOWN evil as much as Obama but if he doesn't get defeated he will have a chance at 8 years of KNOWN evil.
3. Four years of known evil is better than 8 years of known evil. (The lesser of two evils, anyone?)
4. Obama, if re-elected, will be opposed by a Republican Congress and (hopefully) by a Republican Senate.
5. Romney, if elected, will do the same as Obama ("replace" Obamacare with Romneycare, for one) but won't be opposed by a Republican Congress.
6. Opposed evil is better than unopposed evil. (The lesser of two evils, again.)
7. Obama, if re-elected, will be a lesson to the GOP establishment pigs: No more RINOs. The GOP will be defeated but wiser.
8. Romney, if elected, will only show that the GOP establishment is very good at manipulating our vote. The GOP will be victorious but more foolish.
9. A defeated but wiser GOP is better than a victorious but more foolish GOP. (There you go again, the lesser of two evils.)
10. Conclusion: While a true conservative can't vote for Obama, in case of a Obama/Romney general election, Obama's re-election is the lesser of two evils.
Still thinking about this. On number 2, anyone nominated by the Democrats or Republicans in the next 100 elections will be a KNOWN evil. On number 4, the Republicans in Congress hardly oppose Obama now so I can't see them doing so if Obama gets reelected. Just look at the bill they just passed to fund the government for the next six months. On number 7, nothing will make the GOP wiser, just more evil, and that includes people like Jim DeMint and Mitch McConnell. On number 10, still not sure if a vote for Obama is the lesser of two evils. I consider them equal evils in their own way.