Associated Press

Given how very close the 2012 presidential race has become, a candidate like Gary Johnson, on the ballot in 48 states, may very well make a difference.

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.

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.

RNC Chairman Reince Priebus characterized Johnson as a "nonfactor," but there's ample evidence the Republican establishment isn't sincere in its dismissal. In Iowa, the Romney campaign "ran what was effectively a surveillance operation" to monitor Johnson's efforts to collect ballot signatures, while in Pennsylvania, GOP officials "hired a private detective to investigate his ballot drive."

The detective flashed an FBI badge -- he's a retired agent -- and asked to see the petitions collected by Johnson canvassers.

And in Michigan, the Johnson campaign filed the necessary paperwork three minutes late, and Republicans used this to block the former governor from the state ballot.

At a certain level, I can understand the concern among GOP officials. The party wants President Obama's critics to have one alternative -- Mitt Romney -- and fear giving voters more options would weaken the opposition to the incumbent. Given how many conservatives have never been altogether thrilled with Mitt Romney, Johnson starts to look like a threat.

But that's not the whole story.

Unlike Virgil Goode's candidacy in Virginia, which will appeal almost exclusively to the far right, Johnson has the capacity to appeal to likely-Democratic voters -- he wants to legalize marijuana, supports marriage equality, and takes a Ron Paul-like approach to foreign wars.

Still, Johnson seems to be rattling Republicans' nerves a lot more than Democrats'. The Libertarian doesn't have much money, and will almost certainly fail to reach more than a few points in any state, but in an exceedingly close contest, his tallies will be worth keeping an eye on.