WASHINGTON — In the first Republican presidential debate, most candidates took a hands-off approach to Donald Trump and hoped the brash billionaire would hurt himself.

Instead, he only got stronger.

Trump’s unexpected durability has led some of his rivals to shift their strategy for today’s second showdown at 8 p.m. on CNN. Now their goal is to engage Trump, without inflicting any damage on their own campaigns.

The change reflects an evolution in the way Trump is viewed within the Republican Party. No longer dismissed as a summer fling for frustrated voters, Republicans increasingly see Trump as a candidate who could remain atop the field for months.

“He’s in complete, total control of the political battle space,” said Steve Schmidt, a top strategist for Sen. John McCain’s 2008 presidential campaign.

Trump will be standing at center stage when the 11 candidates face off at the Reagan Presidential Library in Simi Valley, Calif. The lineup is the same as last month’s opening debate, with one notable addition: Carly Fiorina.