A year ago, Ted Cruz was branded a "wacko bird" among Senate Republicans, a quarrelsome figure with few friends beyond tea party voters in Texas who sent him to Washington.

Jeb Bush, a mainstream conservative with deep family ties to the Lone Star State, seemed like the party's prohibitive favorite.

Donald Trump was hardly a glimmer in voters' eyes.

Now, at the start of 2016, Cruz has rocketed to the lead in critical Iowa GOP caucuses, while Bush seems to be having trouble getting out of park.

Drafting in Trump's aerodynamic slipstream, Cruz has spent much of 2015 methodically calibrating his campaign to meet the longings of an angry Republican base disenchanted with Washington, including his own party's leaders.

With less than a month before voters start to weigh in on the Republican presidential nomination, Cruz now is locked in a two-man contest with Trump for the insurgent wing of the party.

Cruz's rhetoric says he's an outsider. But his campaign - unlike Trump's - has displayed the polished discipline of the longtime Washington player that he is.

Unlike the "flavor-of-the-month" conservatives who jockeyed for position in the last presidential election, Cruz's fundraising and organization suggest a campaign machinery built for the long haul, forcing the GOP establishment to pay attention.

A succession of national polls over the past three weeks confirms Cruz as the top challenger to Trump - positioning him tantalizingly close to unseating the business magnate as the chief instigator in the GOP's anti-Washington revolt, which could swing the Republican nomination.

"Donald Trump has made me very optimistic about 2016," said former Cruz speechwriter Amanda Carpenter, writing Tuesday for the Conservative Review. "He's sent the GOP establishment into such conniptions that they've been forced to consider supporting Ted Cruz."

'Cruzin' '

As he embarks on a "Cruzin' to Caucus" Iowa bus tour next week, the 45-year-old Texan commands what many regard as the most sophisticated campaign apparatus in the GOP field, boasting 160,000 volunteers, chairmen in 171 counties that make up the first four primary and caucus states, and a small piece of Iowa real estate dubbed "Camp Cruz" - a Des Moines apartment building that serves as a dorm for out-of-state campaign workers.

Cruz's 36-county, six-day tour underscores the importance of the ground game in Iowa, a snowy landscape of farms and small towns devoted to the sort of retail politics where personal Pizza Ranch appearances count infinitely more than slick TV ads.

While Cruz also has his sights set on Texas and the South, it is in Iowa on Feb. 1 where he presents the first real threat to Trump's primacy in the race for the GOP presidential nomination.

"If Cruz wins Iowa, what does that do to Trump?" said Geoffrey Skelley of the University of Virginia's Center for Politics. "Especially for somebody who has defined himself as a winner in every way."

Trump's crowds are bigger, commensurate with the lavish media attention he attracts. Cruz follows a more familiar script focused on traditional Republican voters, those who are more likely to go out on a cold Monday night and caucus with their neighbors in a local school gymnasium.

To find them, he plans to roll through all 99 Iowa counties, a tried-and-true sign of respect for Midwestern heartland voters who demand a personal audience with their candidates.

"A true test of a ground game: the ability of campaigns to identify, win over, and deliver voters," Cruz's campaign said in a recent email to supporters.

Analysts say it's a gradual process that helps explain Cruz's late surge in the race, particularly in Iowa, the only state where he leads in some polls.

"He takes the long-term view of this process, which is exactly what he did in the 2012 Senate race, where he came out of nowhere and was able to steadily build up a coalition," said Brandon Rottinghaus, a political scientist at the University of Houston.

Tortoise and hare

Rottinghaus sees Cruz playing the tortoise to Trump's hare. "He's taken the slow and steady approach to building an organization, raising money and connecting with voters."

Cruz also has mounted an incremental rollout of endorsements from prominent Iowa conservatives, from U.S. Rep. Steve King to evangelical leader Bob Vander Plaats.

A typical endorsement was Monday's testimonial from Iowa activist and blogger Shane Vander Hart, who made an indirect reference to some of the Washington invective aimed at Cruz, such as Sen. John McCain's "wacko bird" swipe.

"He certainly has not won any popularity contests in DC," Vander Hart wrote. "But, in my opinion, he has all of the right people mad at him."

Trump, largely self-funding his campaign, has been able to skip some of those organizational steps, though some of his more enthusiastic supporters have sent money anyway.

At last count, Cruz had raised more money than anyone except Bush and Hillary Clinton, much of it from small-dollar donors.

The difference in style has led to questions about whether Trump devotees, some number with little or no experience in voting, will turn out when it counts.

To Craig Robinson, editor of The Iowa Republican and a former state GOP official, it now comes down to Trump's cadre of disaffected new voters versus Cruz's equally disaffected supporters who know where and how to caucus.

Robinson gives the edge to the Texan.

"I'm comfortable saying that Cruz is the front-runner in Iowa," he said.

Right and wrong

Robinson attributes Cruz's rise in part to the surprising lack of meaningful competition for Iowa's vast trove of social conservative voters - who now appear to have abandoned slumping retired neurosurgeon Ben Carson.

The past two Iowa GOP caucus winners, Mike Huckabee and Rick Santorum, have failed to revive their faith-based candidacies. Cruz also benefited in 2015 by the early exits of former Texas Gov. Rick Perry and Wisconsin Gov. Scott Walker, once a poll leader in Iowa.

A Super PAC backing Huckabee has run a last-ditch radio ad in the last week to weaken Cruz's hold on evangelicals. It questions the Texan's emphasis on constitutional conservatism, which argues that, under the 10th Amendment, states are free to make their own decisions about same-sex marriage.

"If issues like marriage and the sanctity of life are truly issues of principle and not just politics," Huckabee said in a statement, "then there should be no geographical boundaries to what is right and wrong."

But the attack is unlikely to do much for Huckabee, who has consistently polled in the low single digits.

Nor is it likely to hurt Cruz with the competition he's got left, according to Robinson: "It's not like somebody's going to look at this and say, 'Gee, I'm going to vote for Marco Rubio,' or 'I'm going to vote for Donald Trump.' "

'Maniac'

The choice between Cruz and Trump was not always binary. Their appeals largely overlapped, and both were happy to leave it that way - until early December, when Cruz broke into second place in national poll averages. That's when Cruz, speaking at a closed-door fundraiser in New York, questioned Trump's "judgment," prompting Trump's retort that Cruz is "a little bit of a maniac."

Until the rivalry broke into the open, analysts saw Trump as more of a help than a hindrance to Cruz, who seemed content to sit back and hope for the brash billionaire to fade on his own.

"All the focus on Trump has allowed Cruz to take a lot of the things Trump has been saying, use his rhetoric to get close to Trump, but not go all the way," Skelley said. "He hasn't gone 'Full Trump.' "

With Trump in front to take the hits, Cruz has been able to better control his own campaign narrative, relatively free of the scrutiny that comes with front-runner status.

Cruz's surge could change that dynamic, particularly if his opponents decide to dwell on a Washington résumé that covers all three branches of the federal government: Supreme Court clerk, Bush administration lawyer and U.S. senator.

While his Ivy League background and government career might belie all the tea party rhetoric, it adds an aura of plausibility and gravitas to his White House bid.

"He's enough of a politician, a skilled politician, to inhabit both worlds," Skelley said.

Those two sides of Cruz came together on Oct. 28, when he delivered a breakout debate performance in Colorado by slamming the CNBC panel.

"Let me say something at the outset," Cruz said, brushing aside a question about the debt limit. "The questions asked in this debate illustrate why the American people don't trust the media."

The angry Cruz broadside, met with cheers, coincided with the start of his climb in the national polls, from an average of 6.6 percent - below Rubio and Carson - to his most recent average of 18.6 percent. That's good enough for second place - albeit a distant second - to Trump's 35.6.

"That was a turning point for him," Rottinghaus said. "It was where the Cruz he wants to be and the Cruz he actually is kind of met, and he was able to explode."