President Barack Obama set Twitter afire Wednesday with his #my2k hashtag, designed as another weapon in the war of public opinion over tax rates and the fiscal cliff. But one opponent of his tax plan got in on the action too.

The president highlighted #my2k in his late morning remarks on taxes, encouraging people to tweet what they would do with an extra $2,000 resulting from a proposed extension of current middle-income tax cuts (while letting cuts on households’ income above $250,000 expire). Mr. Obama also tweeted it out to his more than 20 million Twitter followers. Tweets flooded in, pushing the #my2k hashtag to the top of Twitter trends.

The wrinkle: The Heritage Foundation bought the “promoted tweet” for the term – meaning anyone reading the #my2k hashtag’s thousands of tweets would see the conservative group’s ad right at the top – in this case, a promotion for a blog post on “4 reasons why Warren Buffett is wrong on tax hikes!”