Republican presidential candidate Donald Trump was endorsed Saturday by former Arizona governor Jan Brewer, whose hard-line positions on immigration reform and tussles with President Obama catapulted her to national prominence during her two terms in office.

“A nation without borders is like a house without walls – it collapses. As Arizona’s Governor, I witnessed too much heartache, loss and suffering caused by illegal immigration,” Brewer said in a statement announcing her endorsement. “For years I pleaded with the federal government to do their job and secure our border. Today, we can elect a President who will do just that — Donald J. Trump.”

With her endorsement, Brewer delivers Trump the support of a former two-term governor with outsize credibility on immigration issues among Republicans. But she is also someone who managed to walk the fine line Trump seeks as he inches toward the GOP nomination: a prominent voice in the party whose frequent battles with the conservative establishment made her a populist favorite.

The former governor was at the center of a heated debate over immigration reform when she signed a controversial enforcement bill into law in 2010, which was later partially struck down by the Supreme Court. She and Obama generated headlines in 2012 when they were seen engaging in a heated discussion on a Phoenix airport tarmac during a visit by the president.

But she angered Republican leaders in 2013 when she moved forward with a Medicaid expansion plan facilitated by the Affordable Care Act, Obama’s signature health-care law. She argued at the time that it was the best thing for her constituents, regardless of conservative opposition to the law itself.

Brewer, who left office in January 2015, is the latest in a series of high-profile Republicans to endorse Trump, whose insurgent White House bid has been met with apprehension by Republican establishment leaders who fear the billionaire could doom the party’s chances during the general election.

New Jersey Gov. Chris Christie became the highest-ranking official to endorse Trump on Friday, calling him the only candidate left in the GOP race who can beat Democratic front-runner Hillary Clinton in the fall. Christie’s endorsement opens the possibility that many more establishment Republicans will throw their support behind Trump as he inches closer to the Republican nomination.

“I love the state of Arizona and have received incredible support throughout the state,” Trump said in a statement. “I am leading in all the polls and we have had amazing events with tremendous crowds. I am honored to receive this endorsement from Governor Brewer.”