But, you might wonder, who is Mike Pence, anyway?
Relatively obscure nationally but well-known in political circles for years, Pence’s career trajectory has seemed to mirror the evolution of the Republican Party as a whole. He went from heading a free market think tank to hosting a talk radio show. He went from criticizing Republican leadership from the right to becoming the establishment himself.
All the while, Pence has been deeply conservative. His selection was a sign that Trump was trying to embrace the modern Republican Party — or at least build bridges to it — rather than emphasizing his differences with it.
And it largely seems to have paid off — most Republican voters have rallied to support Trump rather than continuing to hold out after the divisive primary season.
1) Pence used to be a conservative outsider — but the Republican Party has moved toward him
Pence came up in politics as a conservative outsider. As a young lawyer, he failed to win election to Congress in two early campaigns, in 1988 and 1990. Afterward, he became the head of a free market think tank, the Indiana Policy Review Foundation, and then a talk radio host.
When Pence finally made it into Congress in 2001, he became a frequent critic of his own party’s leadership for being insufficiently conservative, and chaired the far-right Republican Study Committee. He criticized President George W. Bush’s push to add prescription drug coverage to Medicare, and when the job of House Republican leader opened up in 2006, Pence challenged John Boehner for the job — and lost in a landslide.
But Pence won in the long run. Resistance to Obama’s policies combined with the rise of the Tea Party to push the GOP further to the right. Pence’s very conservative economic and social issue positions are no longer considered fringe in the party. Now, while he’s still a conservative, he’s squarely in the party’s mainstream.
2) Mike Pence is really, really anti-abortion and a longtime critic of Planned Parenthood
One example that illustrates how Pence and his idea went from a conservative outsider to the GOP mainstream is his idea to defund Planned Parenthood.
As Sarah Kliff has written, Pence started going after the pro-choice organization’s government funding in 2007 and kept pushing it afterward. Eventually, his party followed — a Pence amendment to defund Planned Parenthood passed the House in 2011 (though it was never signed into law due to Democratic opposition).
And since Pence became governor of Indiana in 2013, he’s continued to fight for pro-life causes. In 2016, he signed a bill into law that banned abortions for reasons of genetic anomaly and created a new requirement to bury or cremate all fetal remains, as Emily Crockett has written.
3) Last year, Pence was at the center of intense controversy over whether Indiana’s "religious freedom" law was anti-LGBTQ
For a few weeks in early 2015, Gov. Pence was embroiled in a nationwide controversy over LGBTQ rights. In March of that year, he signed the Religious Freedom Restoration Act into law — a bill that, in German Lopez’s words, "says government can't intrude on a person's religious rights unless it has a compelling government interest and is acting in the least intrusive way possible."
Though Pence denied the bill had anything to do with LGBTQ rights, critics feared it would excuse discrimination on religious grounds — for instance, that a baker could refuse to sell a wedding cake to a same-sex couple. Activist groups, celebrities, and even some businesses threatened to boycott the state, until eventually Pence signed a "clarification" to the bill that made clear the bill couldn’t be used as an excuse for discrimination.
4) Mike Pence supported Obamacare’s Medicaid expansion
But Pence hasn’t always stuck with conservative dogma. Although Tea Party governors in other red states were rejecting Obamacare’s Medicaid expansion, Pence himself signed on to it.
In doing so, he won some concessions from the Obama administration on how the expansion would work in Indiana, including requiring beneficiaries to pay into a health savings account. And his administration is currently battling with federal regulators on oversight of the program.
Still, the initial decision showed some flexibility, rather than ideological rigidity, from Pence — he wasn’t so hell-bent on opposing Obamacare that he’d reject millions of federal dollars that could help his state when a compromise could be reached.
5) Mike Pence backed Cruz in the primaries but made it very clear he also thought Trump was great
For the first few months of this year, as establishment Republicans panicked that Donald Trump was running away with their party’s nomination, Pence boldly stayed neutral. Trump had gained a commanding lead by the time Indiana’s May 3 primary was getting close, but Cruz remained in the race, and Pence was heavily pressured by conservative allies to take a stand for principle and back Cruz.
Shortly before Indiana was to vote, Pence did end up endorsing Cruz — but when he announced his decision on a radio show, he accompanied it with some lavish praise of Trump. "I particularly want to commend Donald Trump, who I think has given voice to the frustration of millions of Americans with the lack of progress in Washington," Pence said. Four days later Trump won Indiana easily, and Cruz unexpectedly dropped out of the race that very night.
6) Just 16 years ago, Mike Pence was still arguing that "smoking doesn’t kill"
During the controversy over Indiana’s religion freedom law, Andrew Kaczynski of BuzzFeed News dug up some old postings Pence had written around the time of his 2000 campaign for Congress. "Despite the hysteria from the political class and the media, smoking doesn’t kill," Pence wrote in one.
His evidence for this: "2 out of every three smokers does not die from a smoking related illness." Uh, what about the other one out of three? (Also, don’t miss Pence’s musings on the popularity of the film Titanic — he thought the ship sailing toward an iceberg resonated with audiences because it symbolized America abandoning its traditional values.)
7) Mike Pence was in danger of losing reelection for governor this year
To be Trump’s running mate, Pence has to abandon his own bid for reelection as governor this year, according to Indiana state law — meaning that if Trump loses, Pence will be unemployed without a clear next move in politics.
But apparently, one reason Pence is willing to take that risk is that he’s not really all that confident that he’d win reelection as governor, according to National Review’s Eliana Johnson.
Back in 2012, Pence beat his Democratic opponent for governor, John Gregg, by only 3 percentage points — even though President Obama lost the state by 10. And now Gregg is running again, after a term in which Pence has been weakened by controversy.
Conveniently, a vice presidential nomination allows Pence to slide out of the governor’s race without losing. And if the Trump-Pence ticket does lose, well, Trump would get most of the blame, and Pence would have gained national fame that could make him pretty well-positioned for a potential 2020 presidential bid of his own.
This piece was updated with Trump's official announcement.