DES MOINES, Iowa - He could easily win the Iowa precinct caucuses Tuesday, which kick off the voting for the 2012 Republican presidential nomination.

Yet Ron Paul is largely getting a free pass from his rivals and their supporters, the only top-tier candidate who is escaping the high-profile attack ads flooding the state's airwaves.

Why? Because none of his competitors sees the Texas congressman as a serious long-term rival for the nomination. One, Mitt Romney, sees a Paul win in Iowa as the next best thing to a Romney win, something that would deny an Iowa launching pad for a more serious long-term challenger such as Newt Gingrich or Rick Perry.

"Ron Paul is actually helping Romney," said Craig Robinson, editor of the Iowa Republican website and former political director of the Iowa Republican Party. "Ron Paul is Romney's greatest ally."

Gingrich did criticize Paul in an interview this week with CNN, saying he wouldn't vote for Paul if he were the party's nominee. "It's very difficult to see how you would engage in dealing with Ron Paul as a nominee," the former House speaker said.

And Rep. Michele Bachmann (R., Minn.) hammered Paul's isolationist approach to foreign policy during an Iowa debate Dec. 15.

But neither is backing up those charges with paid advertising. The ads from candidates and groups that support them barely acknowledge Paul.

'63 years'

The only ad now airing that remotely attacks Paul does it obliquely, showing his picture alongside pictures of Bachmann, Gingrich, and former Sen. Rick Santorum of Pennsylvania without naming any one of them individually.

"If Washington's the problem, why trust a congressman to fix it?" says the ad, from Perry, the Texas governor. "Among them, they've spent 63 years in Congress, leaving us with debt, earmarks, and bailouts."

It's not that Paul isn't a threat to win Iowa.

Two new polls Wednesday found him neck and neck with Romney atop the field.

One, from Public Policy Polling, a Democratic firm, showed Paul with the support of 24 percent of likely caucus attendees, Romney with 20 percent, and Gingrich with 13 percent.

Another, from CNN, showed Romney with 25 percent, Paul with 22 percent, Santorum with 16 percent, and Gingrich with 14 percent.

Also, Paul has a deep statewide organization to get people to take part in the caucuses, town-hall-like meetings in which it's crucial to know the rules.

His rivals might be hoping that the news media will do the work for them.

'The calculation'

More important, none of the Republican candidates feels the need to spend ad money knocking Paul down.

That's most true for Romney and the independent group that supports him.

Long suspect to conservatives, the former Massachusetts governor wants to keep conservatives divided and doesn't want to hasten the day that they coalesce around one candidate, particularly Gingrich or Perry.

Though each has problems - Gingrich also raises alarms with conservatives and Perry stumbled through debates - they have the national name or access to money to wage a long-term challenge to Romney.

Paul, on the other hand, might not be able to rally the conservatives who dominate the party. His vow to slash federal spending by $1 trillion in one year is popular among them. But his promise to pull back U.S. forces from overseas, and keep them home, is anathema in the broader party.

"I don't think conservatives would embrace Ron Paul as the standard-bearer," said Keith Appell, a Virginia-based conservative strategist.

"The calculation is that it's not going to be Ron Paul, so why antagonize his people? They're looking to bring them into their tent later."

Johnson Runs as Libertarian

Former New Mexico Gov. Gary Johnson, a long-shot candidate for the GOP presidential nomination, said Wednesday he was leaving the GOP to run as a Libertarian.

Johnson told a news conference at the state Capitol that he was "deeply disappointed" by the treatment he received in the Republican nomination process.

Johnson has been excluded from all but two GOP presidential debates. He has barely registered in the polls.

He said that if he earned the Libertarian Party's presidential nomination, he would appear on the ballots in all 50 states and not be "held hostage to a system rigged for the wealthiest and best-known candidates in a handful of states who happen to have early primaries."

Johnson, 58, is fiscally conservative but supports legalizing marijuana and abortion rights. - AP

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