Marco RubioMarco Antonio RubioGOP group calls on Republican senators to stand up to McConnell on election security in new ads What the gun safety debate says about Washington Trump moves forward with F-16 sale to Taiwan opposed by China MORE on Tuesday officially won the endorsement of Rep. Trey GowdyHarold (Trey) Watson GowdyRising star Ratcliffe faces battle to become Trump's intel chief Cummings announces expansion of Oversight panel's White House personal email probe, citing stonewalling Pelosi says it's up to GOP to address sexual assault allegation against Trump MORE, the chairman of the Select Committee on Benghazi, as the two hit the stump together in Iowa.

“It’s not my job to tell you who to vote for, but I’m going to tell you who I’m going to vote for,” the South Carolina congressman said while introducing Rubio at a town hall event.

“I’m going to vote for Marco Rubio, and I'll tell you why. National security and public safety are the most important issues to me and there is nobody better on those two issues than Marco Rubio.”

He immediately chided President Obama, who has filled out his NCAA basketball bracket on ESPN each year of his presidency.

"Our Founding Fathers did not give us a commander-in-chief to fill out March Madness basketball brackets, or to sample every golf coast on the Eastern seaboard," Gowdy said.

"The most precious things in my life are my wife and two children, and I trust Marco Rubio to lead a country safely that has [the] most precious things in my life in it."

Gowdy's support could be crucial in South Carolina — the third nominating state — and could bolster Rubio’s credentials with the party's base, even as rival Sen. Ted CruzRafael (Ted) Edward CruzIs this any way for NASA to build a lunar lander? GOP strategist predicts Biden will win nomination, cites fundraising strength 3 real problems Republicans need to address to win in 2020 MORE (R-Texas) takes shots at his conservative credentials.

Gowdy noted his role as the chairman of a House Judiciary subcommittee on immigration as he lauded Rubio's commitment to border security in light of the recent spat with Cruz.

"If I were not convinced that Marco Rubio was the person to ensure border security, interior security, and employment security, I wouldn't be wasting your time," he said.

And Gowdy joked that he knew Rubio is a true fiscal conservative after he gave him a campaign tie for Christmas.

“The wrapping paper cost more than the tie,” Gowdy joked.

Over the weekend, TownHall.com first reported that Gowdy would endorse Rubio as he hit a three-day swing in Iowa with the White House hopeful, but Tuesday marked the official confirmation of that report. The announcement was supposed to come during an event Monday, but the campaign cancelled it due to severe weather in Iowa.

Gowdy has earned praise from conservatives for his work on the committee, but drawn the ire of Democrats who believe the panel is targeting Democratic frontrunner Hillary ClintonHillary Diane Rodham ClintonTrump takes aim at media after 'hereby' ordering US businesses out of China Trump knocks news of CNN hiring ex-FBI official McCabe Taylor Swift says Trump is 'gaslighting the American public' MORE ahead of 2016. A Rubio staffer introducing Gowdy noted that his investigation is "exposing the incompetency of not only the Obama administration, but Sec. of State Hillary Clinton."

Soon after the town hall ended, Gowdy hit Rubio's supporters with an email soliciting donations.

This story was updated at 3:28 p.m.