The editorial board of the Des Moines Register, Iowa's most circulated newspaper, is calling on Republican presidential candidate Donald Trump to exit the race.

Though Trump is frequently in the top two of national polls and also a new Monmouth University survey of Iowa Republican voters, the Register said Trump did irreversible damage to his candidacy when he questioned Arizona Sen. John McCain's status as a "war hero."

"Trump, by every indication, seems wholly unqualified to sit in the White House," the Register said in a Monday editorial. "If he had not already disqualified himself through his attempts to demonize immigrants as rapists and drug dealers, he certainly did so by questioning the war record of John McCain, the Republican senator from Arizona."

Calling Trump a "feckless blowhard," the Register said he can serve his country best "by apologizing to McCain and terminating this ill-conceived campaign."

Trump's remarks on McCain, a Vietnam War veteran who has criticized Trump, came at an event in Iowa. During a Q&A, Trump said McCain was captured and "I like people that weren't captured."

The Wall Street Journal's editorial board and Rick Perry, also a GOP presidential candidate, have likewise called on Trump to withdraw from the race.

Trump has since said he would "take it back" if he was misunderstood but has maintained that he was not saying that McCain isn't a war hero.

Iowa is viewed by many Republican presidential campaigns as a critical early primary state in the race for the White House. Winning the state in early 2016, or at least performing well, can offer campaign's the needed momentum to continue into other states.