President Obama's renewed attempt to raise taxes on the rich is facing opposition from Republicans, but, less predictably, it's also alienating several powerful Democrats. While Obama wants to let the Bush-era tax cuts expire for everyone with incomes above $250,000, members of the president's own party who are locked in tight House and Senate races say they'd rather kill the tax breaks only for those earning $1 million or more. Why are some Democrats abandoning Obama on such a major issue? Here, three theories:

1. Obama's plan is poison in swing states
These Democrats obviously know something Obama doesn't, says Paul Mirengoff at Power Line. Three of them — Florida Sen. Bill Nelson, former Virginia Gov. Tim Kaine, and Rep. Shelley Berkley in Nevada — are Senate candidates in closely fought contests. They know their swing states better than Obama does. The fact that they're not on board is a pretty clear indication "that Team Obama's decision to raise taxes for people making more than $250,000 is likely to hurt Obama in states, and among voters, that he needs to win."

2. Many Democrats have always focused on millionaires as the cut-off point
Democrats haven't abandoned Obama — they've always insisted that only the super rich should pay more, says the Tampa Bay Times in an editorial. "If Obama were interested in resolving the fate of the tax cuts before the election, he would call for them to expire at the end of the year for anyone earning more than $1 million." That's a threshold favored by nearly all Democrats. Instead, Obama is starting yet another political "kabuki dance" that can't succeed in Congress. He just wants to motivate "partisan supporters and campaign contributors."

3. Raising taxes in this economy is just a bad idea
Give the dissenting Democrats some credit, says Daniel Halper at The Weekly Standard. Like pretty much everyone in the Republican Party, they recognize that raising taxes "in the middle of poor economic times" would be a disaster. And it's not just moderates. Liberal stalwarts, including House Minority Leader Nancy Pelosi (D-Calif.) and Sen. Chuck Schumer (D-N.Y.) don't want anyone making less than $1 million to pay more. When "even Democrats like Nancy Pelosi believe Obama's tax hikes efforts are misguided," you know it's a non-starter.

Read more political coverage at The Week's 2012 Election Center.