Vermont Sen. Bernie Sanders said in a radio interview that he's thinking about trying to encourage somebody to run against President Obama in a primary election, claiming the president has drifted toward Republican positions because "no one will stand up to him."

Republicans hardly feel that Obama is on their side. House Speaker John Boehner, after splitting off from White House-led debt talks, said Sunday that they are almost "from two different planets."

But Sanders, an Independent, said Friday that the president is not living up to his campaign commitments on issues like Social Security -- reflecting a concern among some Democrats that Obama is willing to negotiate away changes to entitlements to appease Republicans.

Sanders said his "suggestion" is that Obama face a Democratic challenger in 2012.

"I think one of the reasons the president has been able to move so far to the right is that there is no primary opposition to him and I think it would do this country a good deal of service if people started thinking about candidates out there to begin contrasting what is a progressive agenda as opposed to what Obama is doing," Sanders said on radio host Thom Hartmann's show.

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Sanders, while left of most elected Democrats, is an independent and could not step up to the plate to challenge Obama unless he registered as a Democrat.

He showed no interest in doing so, but said he is "giving thought" to encouraging someone else to run.

"There are a lot of smart honest, progressive people who I think can be good presidents," he said. "This is an issue ... we are beginning to talk about a little bit."