The frenzy to purge the presidential campaigns of lobbyists is descending on two new suspects, a key fund-raiser for the Democratic convention set for Denver in August and a former White House counsel vetting possible running mates for Senator McCain of Arizona.

While Senator Obama ordered the Democratic National Committee last week to stop taking donations from lobbyists, the co-chairman and lead fund-raiser for the host committee for the Denver convention, Steven Farber, is a lawyer and federally registered lobbyist with Brownstein Hyatt Farber & Schreck LLP, a firm with offices in Denver, Washington, and elsewhere.

“Not only that, they’re a donor,” an advocate of tighter regulation of political funding, Stephen Weissman of the Campaign Finance Institute, said, pointing to the firm’s logo among several dozen “partners” on the host committee Web site.

“Barack Obama’s failure to meet his own standards concerning the special interests running his party and campaign demonstrates the weak leadership defining his candidacy,” a spokesman for the Republican National Committee, Daniel Diaz, said.

A spokesman for Mr. Obama, Thomas Vietor, said allies of Mr. McCain had no credibility on the issue because the senator from Arizona has counted dozens of lobbyists among the ranks of his senior campaign staff and fund-raisers even though he railed against what he called the “iron triangle of money, lobbyists, and legislation.”

Mr. Vietor said Mr. Obama has been candid that the donation ban he announced is not a cure-all. “It’s not a perfect solution or even a perfect symbol for the problem of lobbyist influence, but it’s a sign of his commitment and it’s certainly a strong contrast with Senator McCain’s campaign, which is paid for and run by Washington lobbyists.”

The Obama campaign also turned the tables on Mr. McCain and his aides for attacking a member of Mr. Obama’s vice presidential vetting team who once headed Fannie Mae, James Johnson, over his ties to a struggling subprime lending firm. Mr. Vietor noted that the Washington lawyer handling Mr. McCain’s vice presidential search, Arthur Culvahouse of O’Melveny & Myers LLP, is a former lobbyist and longtime Washington insider.

“It’s the height of hypocrisy for John McCain … to criticize Senator Obama when the person vetting his own vice presidential nominees has worked for Fannie Mae and whose firm has represented Exxon and even Enron executive Jeff Skilling,” Mr. Vietor said.

One prominent criminal lawyer said it was fair to critique Mr. Culvahouse for his lobbying work, but not for his or his firm’s criminal clients, such as Skilling. “Our Constitution says this man has a right to be represented, whether you like Jeff Skilling or not,” a former president of the National Association of Criminal Defense Lawyers, William Moffitt, said. “If lawyers were disqualified based on whom they represent, there’d be no end to that. … As much as I support Barack Obama, if I were advising him, I’d tell him to get off of that.”

According to records filed on Capitol Hill, the Democratic fund-raiser in Denver, Mr. Farber, is presently a registered lobbyist for the National Association of Home Builders. His firm’s past and present corporate clients run the gamut from United Airlines to Google to the Private Equity Council. Some of the firm’s lobbying clients, such as The New School, the Girl Scouts, and the Simon Wiesenthal Center, are hard to paint as part of the corporate power structure.

“I can’t say I haven’t lobbied on federal issues in the past. I am not now currently doing it,” Mr. Farber said in a telephone interview yesterday. He said no one from Mr. Obama’s campaign had told or urged the committee to steer clear of lobbyist money. “Nobody has contacted us from the Obama administration about what they prefer with us or not prefer with us. I’d welcome the discussions,” Mr. Farber said.

A Democratic Party official said yesterday that the host committee is a “completely separate” entity. However, Mr. Weissman said the local group is effectively under the control of Mr. Obama and the Democratic Party. “They really have the capacity to put on any restrictions they want,” Mr. Weissman said.

In 2000, the host committee for the Democratic National Convention in Los Angeles had a policy of rejecting money from tobacco companies and gun manufacturers. In Boston in 2004, the Democrats quietly reversed the tobacco policy, taking over $120,000 from Altria, formerly Philip Morris. Republicans never announced such a ban and took more than $142,000 from Altria that year.

A spokeswoman from the host committee for the Republican convention in Minneapolis had no immediate answer last night on whether any industries or companies were barred from donating. However, Mr. McCain did signal a lobbying standard last month when he accepted the resignation of the Republican convention coordinator, Douglas Goodyear, following a Newsweek report that the longtime lobbyist once represented the military junta in Burma. Aides said the senator was angry on learning of the Burma tie.

Large energy, drug, and insurance companies are among the announced donors for this year’s meetings in Minnesota and Colorado.

Mr. Weissman said he saw no principled reason to ban or refuse corporate and lobbyist donations to parties and to reject involvement of lobbyists in party fund-raising, but allow all those things to fund the conventions. “The logic is a political logic,” he said.

Mr. Farber said he is racing to meet a Monday deadline to raise $40.6 million in cash for the Denver confab. So far only about $26 million of that is pledged, plus $15 million in in-kind gifts. “I’m not going to sit still until the money’s raised. I’m very encouraged,” he said.