Conservative Wall Street Journal columnist and former Reagan speechwriter Peggy Noonan said Donald Trump doesn't have what it takes to win the White House.

In her latest column, Noonan wrote that the celebrity businessman has been unable to "take yes for an answer" from the voters who made him the Republican presidential nominee.

"This is what became obvious, probably fatally so: Mr. Trump is not going to get serious about running for president," she wrote. "He does not have a second act, there are no hidden depths, there will be no 'pivot.' It is not that he is willful or stubborn, though he may be, it's that he doesn't have the skill set needed now — discretion, carefulness, generosity, judgment. There's a clueless quality about him."

After the GOP convention two weeks ago, Trump enjoyed a slight bump in national and some state-level polls against Hillary Clinton, only to suffer a series of setbacks caused by his own controversial comments.

As a result, his numbers have fallen in more recent polls and Clinton's have risen in light of intense media scrutiny on Trump.

"All the damage done to him this week was self-inflicted," Noonan wrote. "The arrows he's taken are arrows he shot."