In a victory for Republicans and the Obama administration’s conservative critics, Van Jones resigned as the White House’s environmental jobs “czar” on Saturday.

Controversy over Mr. Jones’s past comments and affiliations has slowly escalated over several weeks, erupting on Friday with calls for his resignation.

Appointed as a special adviser for “green jobs” by President Obama, Mr. Jones did not go through the traditional vetting process for administration officials who must be confirmed by the Senate. So it was not until recently that some of Mr. Jones’s past actions received broad airing, including his derogatory statements about Republicans in February and his signature on a 2004 letter suggesting that former President George W. Bush might have knowingly allowed the Sept. 11, 2001, attacks to occur in order to use them as a “pre-text to war.”

Image Van Jones speaking at a conference in Las Vegas last month. Credit... Ethan Miller/Getty Images

Mr. Jones’s involvement in the 1990s with a group called Standing Together to Organize a Revolutionary Movement prompted recent accusations by conservative critics that he associated with Communists. The group, according to a post-mortem written by some of its founders, was an anti-capitalist, antiwar organization committed to achieving “solidarity among all oppressed peoples” with “direct militant action.”