Gary Johnson Libertarian Candidate Worries Republicans Stephen Maturen for The New York Times Backers of Gary Johnson, the Libertarian candidate for president, showed their support in Edina, Minn. When he was running for the Republican presidential nomination last year, Gary Johnson, the former two-term Republican governor of New Mexico, drew ridicule from mainstream party members as he advocated legalized marijuana and a 43 percent cut in military spending. Jim Mone/Associated Press Gary Johnson, the Libertarian Party candidate for president, spoke at Macalester College, in St. Paul, Minn., in September. Now campaigning as the Libertarian Party's presidential nominee, Mr. Johnson is still only a blip in the polls. But he is on the ballot in every state except Michigan and Oklahoma, enjoys the support of a few small "super PACs" and is trying to tap into the same grass-roots enthusiasm that helped build Representative Ron Paul a big following. And with polls showing the race between President Obama and Mitt Romney to be tight, Mr. Johnson's once-fellow Republicans are no longer laughing. Around the country, Republican operatives have been making moves to keep Mr. Johnson from becoming their version of Ralph Nader, the Green Party candidate whose relatively modest support cut into Al Gore's 2000 vote arguably enough to help hand the decisive states of Ohio and Florida to George W. Bush. The fear of Mr. Johnson's tipping the outcome in an important state may explain why an aide to Mr. Romney ran what was effectively a surveillance operation into Mr. Johnson's efforts over the summer to qualify for the ballot at the Iowa State Fair, providing witnesses to testify in a lawsuit to block him that ultimately fizzled. Libertarians suspect it is why Republican state officials in Michigan blocked Mr. Johnson from the ballot after he filed proper paperwork three minutes after his filing deadline. And it is why Republicans in Pennsylvania hired a private detective to investigate his ballot drive in Philadelphia, appearing at the homes of paid canvassers and, in some cases, flashing an F.B.I. badge - he was a retired agent - while asking to review the petitions they gathered at $1 a signature, according to testimony in the case and interviews. The challenge in Pennsylvania, brought by state Republican Party officials who suspected that Democrats were secretly helping the effort to get Mr. Johnson on the ballot, was shot down in court last week, bringing to 48 the number of states where Mr. Johnson will compete on Nov. 6. Reince Priebus, the national Republican Party chairman, has called Mr. Johnson a "nonfactor." And Danny Diaz, a spokesman for the Romney campaign, said that its entire focus was on beating Mr. Obama and that "voters understand the stakes are high, and if they want to change the trajectory of this country, they'll vote for Romney." But Robert Gleason, the Pennsylvania Republican Party chairman, vowing that the state will become far more competitive for Mr. Romney than Democrats realize, said he was not about to give Mr. Johnson an easy opening to play a Nader to Mr. Romney's Gore in Pennsylvania this year. "This election will be close - if you remember, Bush lost by only something like 143,000 votes in 2004," said Mr. Gleason, noting that his party has managed to disqualify tens of thousands of Libertarian signatures. So we play the game hard here. Both sides agree that Mr. Johnson, whose pro-marijuana legalization and antiwar stances may appeal to the youth vote and whose antigovernment, anti-spending proposals may appeal to conservative fiscal hawks - and to supporters of Mr. Paul - has the potential to draw from both Mr. Romney and Mr. Obama. Aides to Mr. Romney, while playing down his impact on their candidate, say Mr. Johnson is more likely to hurt Mr. Obama in the potentially critical state of Colorado, where a marijuana initiative Mr. Johnson supports is expected to draw young voters to his cause on Election Day. They have said they are keeping a keener eye on Virgil Goode of Virginia, a conservative Constitution Party candidate who is on the presidential ballot in Virginia and 28 other states. The Republican efforts to impede Mr. Johnson's candidacy have drawn charges of spying and coercion from Libertarians and countercharges from Republicans that the party had resorted to fraud while accepting secret help from Democrats. Democrats and Obama campaign officials deny any such involvement. But Mr. Johnson has been receiving critical help from Roger Stone, a longtime Republican operative once so committed to his party that he has a tattoo of President Richard M. Nixon on his back.