Former president George W. Bush. (Chip Somodevilla/Getty Images)

A new flier for Jeb Bush's presidential campaign that started hitting mailboxes Thursday includes a letter from former president George W. Bush to Iowa Republicans.

The campaign of the former Florida governor confirmed Friday that the mail pieces should arrive before Monday's caucuses.

In the message, George W. Bush writes that his younger brother "is a tested leader who has made difficult decisions during times of crisis. After 9/11, Florida's economy took a big hit. Jeb acted decisively to rebuild it, ultimately making Florida the national leader in job creation."

"As someone who has sat in the Oval Office, I know Jeb has the leadership skills to grow our economy, fix Washington, strengthen our military and keep America safe," the former president writes.

"On Feb. 1, please caucus for Jeb Bush," he concludes.

News of the mailer was first reported by the Des Moines Register.

It comes about a week after former first lady Barbara Bush sent a similar mailer to Republican voters and appeared in a promotional video for Jeb Bush's presidential campaign.

The video sparked GOP front-runner Donald Trump to mock Jeb Bush for recruiting his "mommy" to help his struggling campaign. Bush responded via Twitter by posting a photo of his mother in eye-black and football shoulder pads, writing "Be careful, Donald."

This week, Jeb Bush said that his brother is expected to campaign for him soon, saying it would be foolish not to make use of a former president who now polls as one of the more popular Republicans in the country.

As for former president George H.W. Bush, he and Barbara Bush were in Washington on Friday to mark the 40th anniversary of his service as director of the CIA.