But just a month later, his quest to stop Donald Trump collapsed.
Cruz lost seven consecutive primaries, culminating with Tuesday's defeat in Indiana that led him to end his run for the Republican presidential nomination.
"Together we left it all on the field in Indiana. We gave it everything we've got," Cruz said Tuesday night. "But the voters chose another path. and so, with a heavy heart but with boundless optimism for the long term future of our nation, we are suspending our campaign."
Cruz's campaign threw everything against the wall as Indiana became a must-win.
He struck a dubious bargain with John Kasich to keep the Ohio governor from campaigning in Indiana -- and failed to effectively court Kasich's supporters. He hastily announced Carly Fiorina as his running mate -- a move seen as desperate and compounded by failing to send Fiorina to the parts of the state where she could help. Even a highly coveted endorsement from Mike Pence lacked pizzazz -- in a radio interview, the Indiana governor first lavished praise on Trump before saying he would vote for Cruz.
And heading into Indiana, Cruz also suffered from a number of cringe-worthy gaffes. Footage of Cruz referring to a basketball "ring" and seemingly failing to notice when Fiorina fell off the stage in front of him trailed the senator as he attempted to break out of his rut.
Finally, he got mad. Tuesday, a visibly frustrated Cruz let loose an angry tirade against Trump Tuesday morning, calling the New York real estate mogul a "pathological liar" and a "narcissist."
"He is proud of being a serial philanderer. ... He describes his own battles with venereal diseases as his own personal Vietnam," Cruz said
Cruz didn't mention Trump during his speech Tuesday night.
In the end, Cruz's defeat boiled down to this: He never fulfilled his promise to unite the religious right with economic conservatives.
The alliance backfired
Ten days before Indiana's primary, Cruz and Kasich announced a potential game-changer: Kasich would skip Indiana to let Cruz have a one-on-one shot at Trump there; Cruz in turn would stay out of Oregon and New Mexico.
Then, Cruz overlooked the most important part: Winning Kasich's voters.
The Ohio governor was most popular among the moderate, fiscal-focused voters in the densely populated, heavily Republican donut counties that surround Indianapolis -- especially Hamilton County to the north and Hendricks County to the west. There, he was seen as a version of Indiana's popular former governor, Mitch Daniels.
Cruz was never a neat ideological fit -- particularly given his penchant for playing up the same social fights over religious freedom and LGBT rights that have battered the popularity of Daniels' successor, Pence.
But his campaign didn't appear to truly court those voters anyway. Instead, the Texas senator spent his time on the trail courting rural, religious voters, and playing defense in urban, industrial areas. He stayed focused on social issues -- with one exception: Cruz borrowed Trump's attack on Carrier, the Indianapolis air conditioning manufacturer that is shipping jobs to Mexico. That message, though, meant little in the well-heeled donut counties.
"Cruz needed to focus more on fiscal issues and national security. Those are the issues that would have appealed to Kasich voters," said Jennifer Hallowell, an Indiana Republican strategist. "I think they perhaps misread the state, or viewed the Republican electorate in Indiana as one-size-fits-all. And Hoosier Republicans are not a monolithic group."
Hallowell added of the alliance: "Kasich voters went running to Trump after that announcement."
Complicating the matter was that Kasich and Cruz downplayed the alliance publicly, making it appear that the campaigns didn't have their act together.
Craig Dunn, the Howard County GOP chairman and a Kasich supporter, said many of the Ohio governor's backers approached him and said: "OK, now who am I supposed to vote for?" That, he said, is because they'd "heard Kasich say, you can go ahead and vote for me."
Deepening Cruz's struggles: He'd tapped into the network of ground troops led by Curt Smith, the head of the Indiana Family Institute. But those volunteers' focus was on the social issues that Cruz already had covered.
"Evan Bayh told me this when I first went to work for him: The key to Indiana is to know that yes, we're a Republican state and we're a conservative state, but we're conservative on money, not social issues," said Dan Parker, the former Indiana Democratic Party chairman, of the former Democratic governor. "And Cruz missed that."
The Fiorina gambit
When Cruz named Fiorina, the former Hewlett-Packard CEO and one-time presidential candidate, as his future running mate, many local Republicans saw it as a big step toward reaching the party's members who were still uncomfortable with Cruz and not ready to back Trump.
"After it was pretty obvious that the Kasich deal backfired, the next opportunity would have been to have Carly Fiorina spend a lot of time in the suburban areas around Indianapolis," Hallowell said. "She appealed to moderate Republicans and women during the debates, and I think had an opportunity to deliver a message and bring folks on board."
After all, Fiorina was an experienced businesswoman who counted Indiana's former lieutenant governor, Sue Ellspermann, among her strong early supporters. And Trump had a weak business record in Indiana, where he'd tried and failed to enter the state's casino business.
But Indiana operatives said they were baffled by how Cruz's campaign deployed Fiorina. Instead of using her as a force multiplier, she largely campaigned alongside Cruz -- and never in the donut counties.
Monday, Cruz's campaign finally changed its approach, sending Fiorina to campaign in the key suburbs of Brownsburg, Carmel and Fishers.
It was, Republicans said, a repeat of the mistake that was already hurting Cruz's campaign.
"I don't know if he took donut county Republican for granted thinking they would vote based on strategy or if he doesn't know how to message to them in a way that's fiscal first, social second," said Pete Seat, a former George W. Bush press aide who's now an Indiana Republican strategist.
The "basketball ring"
As Trump was going five-for-five a week ago in the East Coast "Acela primary," Cruz was already campaigning in Indiana -- in Knightstown, the home of the gym made famous by the 1986 basketball film "Hoosiers."
But he made an awkward rhetorical stumble there, referring to the "basketball ring" instead of the rim.
The next day, Trump rolled out his biggest Hoosier endorsement: legendary Indiana University basketball coach Bobby Knight.
The contrast was stark and immediate. Friday in Evansville, Knight mocked Cruz in an appearance on "Fox and Friends" alongside Trump. "A guy that would come into this state and think that we played with rings instead of baskets is not a guy that's very well prepared to do a whole hell of a lot," the coach said of Cruz.
The episode was damaging because it left Cruz looking like a politician relying on gimmickry -- and with no real response.
Trump had made an even bigger mistake of his own, touting the endorsement of Mike Tyson, the boxer who in 1992 was convicted of rape in Indianapolis.
Indiana Democrats wondered why Cruz didn't hit Trump harder over Tyson -- and lump in Knight, who'd famously declared in 1988 that "I think that if rape is inevitable, relax and enjoy it," and was eventually pushed out of his coaching job after a string of controversies over abuse of players.
"Bobby Knight would be very popular with Trump voters, but he's not very popular with people who actually graduated from IU -- that actually have a degree from Indiana University," said Parker. "Why didn't Cruz put his wife out and say that it's abhorrent that Donald Trump would accept an endorsement from a person that said, a woman should just sit back and enjoy it?"
Trump kept leaning on Knight as his top Indiana surrogate. And soon, he added more well-known former coaches to the mix: Purdue men's basketball coach Gene Keady; Notre Dame men's basketball coach Digger Phelps and Notre Dame football coach Lou Holtz.
Mike Pence: That's an endorsement?
Cruz picked up a big Indiana endorsement of his own when Gov. Mike Pence appeared on the show of Indianapolis talk radio host Greg Garrison -- for former DA who prosecuted Tyson -- and said he'd be supporting Cruz.
It wasn't much of an endorsement, though. Before even mentioning Cruz, Pence heaped praise on Trump, commending him for drawing attention to Carrier's decision to shift jobs to Mexico.
"I know you can't tell a person how to endorse you, but it was an awfully tepid endorsement," said Dunn, the Howard County Republican chairman. "He belabored the point with the wonderful, nice things that Donald Trump had done in terms of bringing voters in -- and then, 'Oh, I don't want to tell people how to vote, but I'm going to vote for Ted Cruz, but I don't want to tell people how to vote.' That's better than nothing, but not a whole lot better than nothing."
While Cruz cut a 30-second TV ad out of the endorsement, Trump once again used what was supposed to be a helpful moment for the Texas senator to mock him.
"All the pundits said, 'You know what, I think that was maybe the weakest endorsement in the history of endorsements,'" Trump told supporters in Carmel on Monday. "In the end, they had to re-run the tape just to find out who he was endorsing."
Pence made things worse in an interview with CNN's Dana Bash, when he made clear that he'd "support the Republican nominee" -- Cruz or not.
The botched Pence endorsement underscored one of the biggest differences between Wisconsin, the site of Cruz's last big Midwestern win, and Indiana: In Wisconsin, he had an aggressive ally in Gov. Scott Walker. In Indiana, the only influential supporter he had was -- with his eyes on his own tough re-election battle against Democrat John Gregg -- eager to avoid alienating anyone in his own party.
Another big difference between Wisconsin and Indiana: Conservative talk radio. Hosts in Wisconsin had unified in an effort to knock off Trump. But in Indiana -- a state where Pence was once the rising talk radio star -- there was no such resistance.
Getting mad too late
On Monday night, Trump packed a huge crowd into one of his signature mega-rallies in South Bend. Cruz, meanwhile, spoke in front of a half-filled room on the state fairgrounds in Indianapolis.
Sensing that the race was slipping away, Cruz by that point had opted for direct confrontation.
Earlier Monday, Cruz sparred with a Trump supporter on live national television in Marion.
In a seven-minute conversation, Cruz asked his heckler to name one thing that he liked about Trump. When the man named "the wall," Cruz said: "Hold on. He told the New York Times editorial board he's not going to build the wall or deport anyone."
The man shouted in his face: "Lyin' Ted!"
And Cruz responded, "Civilized people don't yell. Sir, with all respect, Trump is deceiving you. He is playing you for a chump. Ask yourself two questions: Why is it that the mainstream media wants Donald Trump to be the nominee? And why is that John Boehner supports Donald Trump?"
That was all before Tuesday's outburst, when Trump brought up a National Enquirer report
alleging that it had identified Cruz's father, Rafael Cruz, in a photo with Lee Harvey Oswald months prior to the JFK assassination. CNN has not independently confirmed that report -- and there is no evidence that it is true.
But Tuesday night, all that was left was the end.