Donald Trump's likely vice presidential pick actually didn't vote for him. With the nation's eyes on him this spring, Indiana Gov. Mike Pence (R) said he would be backing Trump's rival, Ted Cruz, in his state's crucial primary.

Indiana's May 3 primary was seen as one of the last chances for the #NeverTrump forces to stop him from winning the primary outright, and Pence had been suspiciously quiet about which side he'd choose.

Four days before the primary, Pence picked Cruz in a somewhat painful decision that we detailed below. Trump would win the state by almost 20 points and Cruz would drop out of the race that night. The original post follows.

With what felt like the entire Republican political world impatiently waiting, Indiana Gov. Mike Pence (R) decided to endorse Ted Cruz on Friday in his state's high-profile primary.

"I'm not against anybody," the governor said in an interview the Friday before the primary with radio host Greg Garrison on WIBC in Indianapolis. But: "I will be voting for Ted Cruz in the upcoming Republican primary."

That simple sentence was not any easy decision for Pence, who waited longer than many in the Republican Party would have liked to make his endorsement. Pence was in the unenviable position of having his state's primary matter more than most to the outcome of this chaotic presidential election while trying to balancing a tricky reelection bid. Stop Trump forces thought (accurately, it turned out) that the Indiana primary could be their last, best shot to deny Trump the nomination outright —and they badly wanted Pence on their side.

But at that moment, Pence was also fifth on our list of the top five most vulnerable governor's seats this year, thanks in part to being at the center of the religious freedom/LGBT rights controversy last year. Endorsing Cruz could have helped Pence overcome sagging approval ratings and win a second term. But we also saw how it can hurt his reelection bid — hence his apparent hesitation to go whole-hog for Cruz.

But the decision was made. Here are the pros and cons of it.

PRO: Cruz is a social conservative. Pence needed social conservatives to be mobilized

Unlike some awkward, ill-fitting endorsements this election, the Cruz-Pence political alliance made sense.

Pence's strong social conservative bona fides suffered somewhat in the aftermath of signing a controversial religious freedom bill last year. He rewrote it to make clear that discrimination against LGBT people is illegal, which some social conservatives interpreted as the governor backing off under pressure from liberal groups.

Pence appeared to regain some ground by recently signing a restrictive (and possibly unconstitutional) abortion law that prohibits an abortion because the fetus may have Down syndrome.

"It makes me want to go knock on some doors for him," Monica Boyer, a tea party activist, told the Indianapolis Star after he signed the bill into law.

But it's possible he thought he needed to do more to mend any hard feelings among his base. Endorsing Cruz, an outspoken social conservative, seemed to go a long way to that end.

CON: His Cruz endorsement could have alienated some

If it's easy to see why Pence's alliance with Cruz won him some voters, it's just as easy to see how it could have alienated others: Moderates. Bob Knight fans. And most especially: The wide range of Trump supporters, including first-time voters.

"The already endangered Pence reelection effort could find itself losing another segment of the Republican base, and the largest, most dynamic one at that," wrote Indiana political columnist Brian Howey.

A WTHR/Howey Politics Indiana poll found that among first-time voters, Trump was ahead 53 percent to Cruz's 25 percent, Howey notes. Those newly engaged voters are exactly who Pence would love to keep active for his campaign in November.

Anytime you endorse in a hard-fought primary, you risk alienating the other guy's supporters. And given who Trump supporters are and how strongly they feel about their candidate, that was doubly true in Indiana.

PRO: Earning goodwill

Pence was under heavy pressure from the Republican establishment to jump on the Cruz train. Like we said earlier, the stop-Trump forces (i.e. most of official GOP) would have loved for Cruz to win the state and its 57 delegates. (Indiana is a winner-take-all system.) They clearly felt they needed Pence on their side for this.

"Ted Cruz and the Party Both Need Your Help, Governor Pence," read a Tuesday editorial in the National Review.

"Why the hell would I ever support Mike Pence again?" wrote Erick Erickson, a prominent conservative blogger on Thursday in a not-so-subtle post expressing his anger that Pence hadn't yet endorsed Cruz. "Either Cruz will win and we can continue the fight to stop Trump or Cruz will lose and more likely than not guarantee a Trump nomination."

If Pence was the focus of GOP ire ahead of his endorsement, he re-entered their good graces by joining prominent current and former governors like Jeb Bush and Scott Walker in endorsing Cruz.

CON: Cruz was in danger of losing Indiana

There was, at the moment Pence endorsed Cruz — with all the risks that come with it — a very good chance that Cruz would lose anyway. A recent Fox News poll showed Trump ahead in the state at 41 percent, with Cruz at 33 percent and Kasich at 16 percent. (The final result was a solid win for Trump: 53 percent to Cruz's 37, with Ohio Gov. John Kasich in the single digits.)

It's not clear how much of an effect Pence's endorsement had on Indiana GOP voters. Only 7 percent in that Fox News poll said they were undecided.

Pence is also wasn't overly popular in the state, with a recent WTHR/Howey Politics Indiana Poll showing his approval rating at 44 percent, with 41 percent disapproving. He was surely much more liked among Republicans than with the state more broadly, but he clearly wasn't the formidable force he was once seen as. Backing the losing candidate didn't help on that front.

PRO AND CON: Pence said he'd still support the nominee (Current verdict: Pro — at least for the moment)

For as many downsides as there are for Pence to endorse Cruz, it could have been even more dangerous for his reelection hopes to be tied to Trump. The presumptive nominee is incredibly unpopular with the general electorate, and Pence -- like many other vulnerable Republican senators and governors up for reelection -- could have used a buffer from him if he's their nominee. Pence's support for Cruz is a very clear way to do that.

But when he endorsed Cruz, Pence also said this:"Whoever wins the Republican nomination for the president of the United States, I'm going to work my heart out to get elected this fall."

Democrats saw that as an opportunity to tie Trump to Pence this fall. So, apparently, did Trump himself.

Pence was forced to pick a side in this contentious Republican race. And he did.