Going into the week, Jeb Bush and Marco Rubio seemed to be the rivalry to watch in the GOP primary. After the fourth Republican debate, that’s been replaced by a new and perhaps more consequential storyline: the coming collision of Rubio and Ted Cruz.

The two Cuban-Americans, both 40-something, first-term senators with tea party credentials, continue to trail outsider candidates Donald Trump and Ben Carson in the polls. But they’re increasingly viewed as the candidates to beat in their respective lanes — Rubio as the new establishment front-runner and Cruz beginning to consolidate support from the party’s more conservative wing. The consensus view that they outperformed their rivals Tuesday has served only to cement that impression.


“There’s this growing sense that Rubio’s the best candidate and that people are getting pretty comfortable with him,” said Bruce Haynes, a Republican strategist. “You can feel Carson and Trump losing support. Cruz is a quiet tide in the night that is beginning to wash out the base on Donald Trump. Now, I think, people are looking at Cruz as the candidate who’s best positioned in a lane to run with Rubio and give him a real fight.”

The two didn’t spar much in Tuesday's debate, but from Cruz at least, the subtext was clear — both during the debate and in his interviews afterwards — as he broached two subjects perceived to be Rubio vulnerabilities: immigration and support for sugar subsidies.

Cruz noted during the debate that he “led the fight against amnesty in Congress with [New York Democratic Sen.] Chuck Schumer and the establishment Republicans,” a veiled shot at Rubio, who co-authored the comprehensive immigration reform proposal that included a path to citizenship for undocumented immigrants.

Rubio, who stayed out of the fray over immigration Tuesday, has since disavowed the 2013 legislation, arguing now for a piecemeal approach that starts with enforcing the country’s immigration laws.

But during a round of TV interviews Wednesday morning, the subject resurfaced as Rubio was pressed on whether he’d overturn President Barack Obama’s executive order that currently shields some 5 million undocumented young people from deportation.

“We need to enforce our law,” Rubio said during an appearance on CBS News.

With the next debate more than a month away and campaigns shifting into a three-month ground war for support in the early states, both candidates face more immediate concerns — specifically, the obstacles in their respective paths.

For Cruz, it’s overtaking Ben Carson in Iowa.

Next week, Cruz will ratchet up his presence there: Cruz’s campaign has dropped $140,000 on television airtime in three Iowa markets starting next week. A super PAC backing Cruz, Keep the Promise III, also appears to have reserved air time from Nov. 16 to Nov. 24, according to a media tracking source, for one-minute spots to run in the same three markets.

It’s the latest salvo from the Cruz campaign in an intensifying effort to compete hard in an early state where Cruz’s conservative message can take root. An August religious liberty rally marked a big public kickoff, and since then Cruz has been a frequent visitor as part of his promise to visit all of Iowa’s 99 counties. The Texas senator has hit remote parts of Iowa and attended higher-profile events, such as a recent pheasant hunt with prominent conservative Rep. Steve King, whose son is involved with the Iowa arm of a super PAC backing Cruz.

A robust field organization is already taking shape. Cruz has campaign chairmen, his campaign says, in every county in each of the first four states. The senator and his father, Pastor Rafael Cruz, are also working to procure endorsements from pastors in each Iowa county as part of his plan to consolidate the evangelical vote. Cruz will again be in the state Nov. 20 for a gathering of Christian conservatives headed by prominent activist Bob Vander Plaats.

King's and Vander Plaats' are coveted endorsements, and Cruz and other conservative candidates are competing hard for their support. In Iowa Republican circles, Cruz is viewed as having a good shot at both. Vander Plaats is expected to announce his position sometime around Thanksgiving.

Ostensibly, Cruz’s Iowa push is about catching up to Carson, who’s leading in polls there, not Rubio. But should Cruz win the state’s first in the nation caucuses on Feb. 1, he could generate enough momentum to cause a serious problem for Rubio a few weeks later in South Carolina — a state Rubio might then have to win.

Rubio’s team is aware of the implications of a Cruz win in Iowa, according to a consultant who has worked with Rubio and is familiar with the campaign's thinking. In part, that may explain Rubio’s campaign swing through the Hawkeye State on Wednesday morning after the debate across the state line in Wisconsin.

Cruz often talks about the GOP primary contest as if it’s a basketball tournament bracket, with lanes for him in the tea party, libertarian and evangelical sections. His campaign sees Rubio as competing in a separate, establishment-focused bracket, and doesn’t see him as an immediate threat. The simple act of labeling Rubio as an “establishment” candidate — as Cruz did in a post-debate interview Tuesday night — is a slight in itself.

“Nobody likes the establishment — no one in the tea party is going to say, ‘I like that establishment guy,’” Rick Tyler, Cruz’s spokesman, said Wednesday. "Voters are saying with such a clear voice to the establishment, ‘Not this time. Not this time’.”

Rubio’s team sees the same lanes — the difference, in their view, is their candidate’s appeal is broad enough to transcend all of the party’s constituencies, unlike Cruz's.

“Marco Rubio is in a unique position to unite the various factions of the Republican coalition,” said Whit Ayres, Rubio’s pollster, who noted focus group data that showed an uptick in support from social conservatives, not just moderate Republicans looking for a candidate who can win the general election.

If Carson wins the first contest on the board, the thinking goes, he’s less likely than Cruz to challenge Rubio as the calendar progresses. Cruz, on the other hand, with a superior field organization, a vast volunteer operation and far more money in the bank, would be in a stronger position to amass delegates as the race broadens in March and April and beyond. Cruz has spent months organizing in states that hold contests later in the calendar, particularly in the South.

Rubio, who's been reluctant to go all-in on any one of the four early contests, flew Wednesday afternoon from Iowa to South Carolina, the third state on the primary calendar and the early state where the Florida senator’s organization is the strongest. The main super PAC backing his campaign has already placed an eight-figure ad buy to reserve TV airtime from late December through the election days in Iowa, New Hampshire and South Carolina.

“This all comes down to winning these early states. The danger for every candidate is to do well but not to win,” said Stuart Stevens, the GOP strategist who guided Mitt Romney’s 2012 campaign. “I’ve always thought the race would come down to Cruz and whoever was going to win [the nomination].”

Daniel Strauss and Steve Shepard contributed to this report.