When Ron Paul leaves office in January, he will have been more successful than many of the legislators who spent decades maligning him. Paul’s ideas have gradually gone from marginal to mainstream, and his record shows how much even a single determined man of principle can do to change a movement. In foreign policy especially, the Texas congressman leaves behind a new generation of leaders, both libertarian and conservative, who challenge the disastrous bipartisan consensus.

A decade ago, only seven Republican members of Congress voted against the Iraq War—six congressmen and one senator. The number of conservative legislators who opposed the war was even smaller still, the redoubtable trio of Jimmy Duncan, John Hostettler, and Paul.

The other dissenters were moderate to liberal Republicans representing districts where George W. Bush and any policy he proposed—much less sending young Americans to die in a war of choice—would have been deeply unpopular. Lincoln Chafee, the only GOP senator to vote against the authorization of force, was the son of the last great Rockefeller Republican and easily his party’s most liberal member of Congress. Connie Morella of Montgomery County, Maryland represented the most Democratic congressional district held by a Republican.

Rounding out this group was the unpredictable Iowan Jim Leach and Amo Houghton, a New Yorker who voted with Democrats on many issues. While Paul, Duncan, and Hostettler all opposed the war from the right, the bare majority of antiwar Republicans opposed it from the left.

Small as this group was, its ranks would soon grow thinner. Morella was defeated in 2002, right after voting against the war, the victim of redistricting by Maryland Democrats. Houghton retired after the 2004 elections. Chafee, Hostettler, and Leach were all defeated in the Democratic tidal wave of 2006.

The Wall Street Journal editorial page surveyed this track record and concluded there was no political benefit for Republicans to turn against what was by then an increasingly disastrous war. These were dark years for antiwar conservatives, when Rudy Giuliani appeared likely to seize the GOP presidential nomination—in spite of his pro-choice stance—on the strength of his hawkishness and 9/11-hero status alone.

As it turned out, Giuliani’s biggest moment in the 2008 primary campaign was an exchange with one of the two surviving antiwar Republicans in Congress. Ron Paul was then in his tenth House term, running for president as practically an asterisk candidate, receiving just 1 percent of the vote in national polls. Giuliani led nationally as late as November 2007, beating new entry Fred Thompson by nine points in Gallup’s polling.

On May 15, 2007, the Republican contenders debated in Columbia, South Carolina. Paul argued that American intervention in the Middle East—bombings, sanctions, and efforts to destabilize foreign governments—helped turn local populations and their co-religionists against us, to the point that they would contemplate terrorist attacks like those on 9/11.

“Are you suggesting we invited the 9/11 attacks, sir?” asked the Fox News moderator. Paul had said nothing of the sort, but neither did he react to the implication behind the question as forcefully as he might have. Giuliani pounced. “That’s an extraordinary statement, as somebody who lived through the attack of Sept. 11, that we invited the attack because we were attacking Iraq,” he said. “I don’t think I’ve ever heard that before, and I’ve heard some pretty absurd explanations for September 11.”

Giuliani waited for the thunderous applause to die down, then demanded a retraction: “I would ask the congressman to withdraw that comment and tell us he didn’t really mean that.” Paul didn’t budge.

The optics were poor: a little-known congressman was standing against the GOP frontrunner on an issue where 90 percent of the party likely disagreed with him. Paul did not do enough to rebut the “blame America first” charge, while Giuliani hit all the right emotional notes. Predictably, there came calls from prominent Republicans over the next few days to exclude Paul from future debates and even throw him out of the party. Giuliani was judged the decisive winner of the exchange.

But then something surprising happened: the encounter helped galvanize a movement behind Paul while Giuliani’s campaign died a slow, painful death. Paul outperformed Giuliani in most primaries and caucuses, wrapping up his first Republican bid for the White House with more than 1 million votes. Giuliani dropped out of the race after the Florida primary and received less than 600,000 votes.

More importantly, Giuliani’s influence waned after his disappointing performance while Paul became something of a GOP rock star. He ran again for president four years later, this time topping 2 million Republican primary votes. He briefly surged to the top of the Iowa polls—eventually finishing a very strong third in the caucuses—and ran second behind Mitt Romney in New Hampshire.

When Ron Paul voted against the Iraq War in 2002, he represented conservative political tendencies from Robert Taft to Pat Buchanan that were on the wane. The conservative magazines, organizations, and third parties that dissented from hawkish foreign policy were uniformly small. There was a concerted effort to marginalize even these few “unpatriotic conservatives.”

Support for the war was not only nearly unanimous within the GOP, but bipartisan. Half the Democrats in the Senate and key Democratic leaders in the House joined Republicans in the march to war. Consider this abbreviated list of prominent Democrats who supported the Iraq War: Joe Biden, Harry Reid, Steny Hoyer, Hillary Clinton, Chuck Schumer, Richard Gephardt, John Kerry, John Edwards, Joe Lieberman, and Robert Wexler. All of these Democratic leaders, many of them potential presidents, had less sense than a congressional backbencher from Texas who mainly wanted to give speeches about Austrian economics.

What began as an academic exercise became a real movement. Paul’s is the only flavor of conservatism that currently appeals to millennials and other young voters. In Iowa, he finished 35 points ahead of Romney among voters aged 17 to 29. In New Hampshire, Paul won more voters between the ages of 18 and 24 than Romney, Rick Santorum, New Gingrich, and Rick Perry combined.

Even in Alabama, a rare state where Paul took just 5 percent of the vote, he did twice as well with voters between the ages of 18 and 29. His worst states were the places where the Republican electorate was old. Paul’s boisterous campaign rallies were filled with young people, as are the conservative and libertarian organizations—such as Young Americans for Liberty—his efforts spawned.

In January, Paul will retire from Congress. A decade ago, this would have signaled the effective end of antiwar conservatism as a meaningful political force. Today Paul leaves behind an entire wing of the Republican Party sympathetic to his views, some of whom identify explicitly as “Ron Paul Republicans,” while some do not.

Justin Amash, a freshman Republican from Michigan, has already emerged as a Paul successor of sorts in the House. Like Paul, he is a constitutional stickler, refusing to vote for bills that contradict his oath to uphold the Constitution. He has pressed for an end to Bush’s wars and opposed Obama’s new one in Libya.

Paul’s son Rand has become the leading Tea Party senator, more widely admired by the broader conservative movement than his father. Reason editor Matt Welch has called him “the most interesting man in the Senate.” He has also become the most vocal conservative Republican opponent of excessive foreign adventurism in that chamber since Robert Taft.

That’s not to say the GOP is Ron Paul’s party. Paul supporters were mistreated by party bosses in primaries and caucuses from Maine to Louisiana. Convention planners in Tampa were short-sighted and brutish in their handling of Paul delegates. But Ron Paul supporters hold important party leadership positions at the state level in Iowa, Maine, Alaska, Nevada, and elsewhere. They have won seats on the Republican National Committee. Paul’s campaign chairman will be running Senate Republican Leader Mitch McConnell’s 2014 reelection campaign.

The number of Republicans who more quietly are coming around to Paul’s positions is growing. Many Republicans who once wanted to read Paul out of the party now embrace him—or at least covet his voters. Former Republican National Committee Chairman Michael Steele went from suggesting in 2008 that Paul was in the wrong party to saying the 2012 convention planners treated him with “rudeness and stupidity.”

“Why would you alienate an individual who has the ability to attract a new generation of voters, who are already skeptical of your institution but are willing to at least listen through the vehicle of this individual and the words that he is saying?” Steele asked on Comedy Central. “Why would you alienate them, get on the floor and not let them speak?”

Even Romney, whose aides were responsible for the “rudeness and stupidity,” has been careful to avoid saying anything critical of Paul. He went so far as to allow a video tribute to a politician who had refused to endorse him to be broadcast during the convention.

Perhaps the most celebrated speech at that convention was delivered by Hollywood actor Clint Eastwood, who unlike the nominee criticized Obama for staying in Afghanistan too long. The crowd laughed and applauded. Some of them might have cheered any anti-Obama jibe, regardless of substance, but it is noteworthy that even in that setting the most popular speaker sounded more like Ron Paul than John McCain.

When Ron Paul’s remarkable congressional career comes to a conclusion, he can return to Texas with the satisfaction of knowing that his educational mission revived an honorable political tradition: an American conservatism dedicated to conserving, not destroying.

W. James Antle III is editor of the Daily Caller News Foundation.