Donald Trump, defying skeptics and overcoming an avalanche of mockery from establishment Republicans, has extended his streak as the party’s presidential frontrunner for almost five months.

With the Iowa caucuses less than two months away, Republican leaders are growing deeply alarmed by Trump’s resilience. Anxious that his lead may not fade before the voting starts, GOP strategists have begun to brace for a long and painful nomination fight, with Trump’s opponents hoping to grind him down over a period of months.

In a new CNN/ORC poll released Friday, Trump leads the GOP field of White House hopefuls at 36% — his broadest support this cycle. In a distant second place is Ted Cruz at 16%, giving Trump his widest lead this year, followed by Ben Carson at 14% and Marco Rubio at 12%. Just two days before, a Quinnipiac University poll showed Trump on top at 27%, followed by Rubio at 17% and Carson and Cruz tied at 16%.