CNN, which took criticism for steering the Democratic presidential debate in Las Vegas toward sound bites at the expense of substance, is also catching heat for its handling of the Republican presidential debate that was based on questions posed through YouTube.

For starters, since CNN producers selected the questions to ask the candidates from among more than 5,000 video entries, it controlled the direction of the debate.

That fact led to the real problem: CNN directed the debate for its own self-serving purposes, says Los Angeles Times media critic Tim Rutten.

He writes that the debate “raises serious questions about whether CNN is ethically or professionally suitable to play the political role the Democratic and Republican parties recently have conceded it.”

The foundation of his scathing criticism is that, playing to the bias of Lou Dobbs in wanting to exploit the immigration issue, CNN dedicated the opening 35 minutes of the debate to the issue — even though the respected Pew Center has found that only 6 percent of persons it surveyed nationally say immigration is the most important electoral issue.

So a disproportionate amount of debate time focused on an issue to promote Dobbs’ agenda, even as most Americans would rather hear the candidates talk about the Iraq war, the economy and health care, Rutten observed.

“CNN has failed in its responsibilities to the political process,” Rutten wrote, “and it’s time for the leaders of both the Republican and Democratic parties to take the network out of our electoral affairs.”