WASHINGTON — It seemed they were the best of friends. Ted Cruz stood on the floor of the Senate and effusively praised his Republican colleague Marco Rubio.
“Senator Rubio is inspiring. Senator Marco Rubio is a critical national leader,” Cruz said, filling time during a 20-hour filibuster in which he also praised Rubio’s life story and his political acumen.
“I don’t know if there is anyone more effective, more articulate, or a more persuasive voice for conservative principles than my friend Marco Rubio.”
But that was two years ago. Now, a rivalry in the Republican presidential primary contest that had been simmering for weeks has burst into public view. Each is competing to take on the role of the best alternative to the front-runner, business and entertainment mogul Donald Trump, and whatever camaraderie they once enjoyed has evaporated.
Cruz and Rubio, who share a Cuban-American heritage, engaged in some of the most heated exchanges of Tuesday night’s GOP debate, a battle that brimmed with intensity and displayed flashes of venom like a sibling rivalry gone sour.
The brawl, which continued into Wednesday, was a preview of what is likely to be a drawnout competition over the next seven weeks, leading up to the Iowa caucus and the New Hampshire primary, as the two freshman senators try to prove their conservative credentials.
The battle also could have implications for Republicans at a time when the party is eager to attract Hispanic voters. Each of them is from a state with a big Latino population — Rubio from Florida, Cruz from Texas.
Rubio went on the attack first Tuesday night when asked by moderators about a difference he has with Cruz on reforming NSA surveillance programs. He tried to keep the feud alive Wednesday by focusing on Cruz’s repeated attempts to cut spending, including some of his votes against defense budgets.
“You know, Ted stood up there and said, ‘I’m gonna utterly destroy ISIS,’ ” Rubio said on Fox News. “Anyone can say that. What are you gonna do it with? And when you support a budget like he does, that dramatically cuts defense spending, when you vote against every defense authorization bill ever presented before you.”
The Cruz campaign on Wednesday night released a statement, headlined “Marco Rubio’s Trouble With the Truth,” challenging several of Rubio’s contentions.
Rubio won his seat in 2010 with support from the budding Tea Party movement. Cruz came in 2012, pledging to remain pure to conservatives and to upend the Washington establishment.
In the years since, Cruz has continued to cultivate Tea Party voters nationally — arguing for government shutdowns to prove his points — while Rubio has sought to broaden his support and, occasionally, work with Democrats.
While Cruz has been openly contemptuous of clubby Senate traditions, Rubio has tried to work within the chamber. Rubio has more allies in the Senate, while Cruz has more often angered his GOP colleagues.
Cruz said Rubio was an ally of President Obama on immigration and at one point declared “Marco knows what he’s saying isn’t true.”
Rubio was a key component of the so-called Gang of Eight, four Democrats and four Republicans who pursued an immigration overhaul that would enhance border security in return for a pathway to legal status for illegal immigrants.
“There was a battle over amnesty, and some chose, like Senator Rubio, to stand with Barack Obama and Chuck Schumer and support a massive amnesty plan,” Cruz said during the debate.
Rubio has argued that Cruz’s position is not that different from his own.
“Did Ted Cruz fight to support legalizing people that are in this country illegally?” Rubio said. “Does Ted Cruz rule out ever legalizing people that are in this country now?”
That spurred Cruz to declare more definitively than he had before that he won’t support any pathway to legalization.
“For Marco to suggest our record’s the same is like suggesting the fireman and the arsonist [are the same] because they are both at the scene of the fire,” Cruz said.
They also disagreed on legislation that passed the Senate this year making it harder for the government to access phone records. Cruz defended his vote in favor of the legislation, while Rubio said it could make Americans less safe.
Following an extended back- and-forth among Cruz, Rubio, and Senator Rand Paul, New Jersey Governor Chris Christie chimed in:
“Listen, I want to talk to the audience at home for a second. If your eyes are glazing over like mine, this is what it’s like to be on the floor of the United States Senate. I mean, endless debates about how many angels on the head of a pin from people who’ve never had to make a consequential decision in an executive position.”
Senator Dean Heller, a Nevada Republican who is backing former Florida governor Jeb Bush, worried about the damage done among Latino voters by Rubio and Cruz working to outflank one another on immigration. Heller said Republicans need to increase their share of the Latino vote from what it was in the last several elections.
“We need north of 40 percent of the vote in order to win this race, and we’re certainly not going to get that with Cruz and Rubio, the two Hispanic candidates out there, as they continue to food-fight over this immigration bill. It’s very, very un-presidential, and it’s not doing them any favors with the community.”
Matt Viser can be reached
at matt.viser@globe.com.
Jim O’Sullivan can be reached at jm.osullivan at globe.com.