Cleveland, Ohio - It was supposed to be Mike Pence's night, his Republican national convention debut as running mate to presidential nominee Donald Trump.

Republicans voiced hopes earlier that his speech on Wednesday night would unite the party following a tense start to the gathering, but these hopes were dashed when former presidential candidate Ted Cruz encouraged Americans to “vote their conscience".

Earlier today, senior campaign manager Paul Manafort called the Indiana governor "dogged," and "a man after Trump's own heart," saying his introduction to the American people tonight would "help us to accelerate the unification of the party in a real, meaningful way".

Instead, Pence's speech was overshadowed by Cruz, who, having refused to endorse the celebrity business tycoon, was booed by delegates on the third night of the convention in Cleveland.

Pence was not Trump's first choice. Many pundits believe that the socially conservative governor was chosen in the hopes that he may be able to get the Republican bigwigs to support this unlikely nominee. But apart from immigration reform, the two don't see eye to eye on much: on social security and Medicare, on trade agreements, and the war on Iraq.

READ MORE: Donald Trump unveils Mike Pence as running mate

"Pence is arguably about the best Trump could do," said Michael Tomasky, editor of Democracy, a quarterly liberal journal.

"Conservatives love him, and he at least represents some kind of tie to the Republican Party establishment. But the two of them come from such completely different worlds and don't have much chemistry."

While Pence – a former congressman – does add a layer of legislative prowess to a campaign that lacks it, his history has also been mired in controversy.

"Pence needs to demonstrate that he brings knowledge, measured judgement and gravitas to the ticket," said Frederick Clarkson, senior fellow at Political Research Associates, a social-justice think-tank.

"As a former six term member of Congress and current governor of a state, we can believe that Pence will do that. But then the question becomes, what is the substance that he brings?"

The man, who described himself as "a Christian, a conservative, and a Republican," came under fire for signing the "Religious Freedom" bill in 2015 that some said allowed businesses to deny services to gays by invoking religious reasons.

"Although abortion rights and marriage equality are part of the unambiguous law of the land, Pence represents the politics of permanent reaction and rollback, seeking to use the tools of government to undermine access to these rights wherever he can," Clarkson told Al Jazeera.

Pence, also a former private attorney and a talk-radio show host, compared a Supreme Court decision to uphold the Affordable Care Act to the 9/11 attacks. As governor, he attempted to forbid Syrian refugees from settling in Indiana, and opposed amnesty to millions of immigrants without legal status.

The Clinton campaign has already accused him of opposing a federal minimum wage hike and signing a law that could allow for Indiana skilled workers to be paid less.

Trump has chosen "an incredibly divisive and unpopular running mate known for supporting discriminatory politics and failed economic policies that favour millionaires and corporations over working families," said John Podesta, chair of Hillary for America.

While Pence has distanced himself from the anti-Muslim rhetoric that has become a hallmark of Trumps' campaign (he described Trump's proposed Muslim ban as "offensive and unconstitutional") some liberals believe that his views do not bode well for American freedoms.

"Mr. Pence brings a distinctly conservative Christian theocratic strain to government and politics, and in that way poses an ongoing threat to the civil and religious rights of all Americans, win or lose in November," Clarkson said.