It is the first time in memory that a sitting national leader of the Republican Party has faced a public challenge over his ideological leadership by conservative members of his own national committee.

Critics say it is also a sign of Mr. Steele’s rocky start as RNC chairman and his continuing struggle to assert control of the party’s message since his election in January.

“The threat to our country from the Obama administration cannot be underestimated,” Indiana RNC member James Bopp Jr. wrote Wednesday in an e-mail to the full RNC membership. “They are proceeding pell-mell to nationalize major industries, to exponentially increase the size, power and intrusiveness of the federal government, to undermine free enterprise and free markets, to raise taxes to a confiscatory level.”