Adam Kinzinger says he should've been 'worried' at how easily he was able to reach Marco Rubio before endorsing him in 2016: 'No presidential candidate should be that available'

• In Adam Kinzinger's new book, he recounts some key moments from the 2016 GOP presidential primaries.
• Kinzinger backed Florida Sen. Marco Rubio after former Florida Gov. Jeb Bush left the race.
• He said he should've been "worried" at how easy it was to text with Rubio about the endorsement.

As the 2016 Republican presidential field took shape, then-Rep. Adam Kinzinger made the decision early-on to get behind former two-term Florida Gov. Jeb Bush, who at the time was widely seen as the favorite for the nomination.

Bush — the son of former President George H.W. Bush and the younger brother of former President George W. Bush — had a well-received executive record, decadeslong party connections, and the fundraising chops that made him the preferred candidate of many traditional conservatives and top GOP donors. But then came businessman Donald Trump, whose entry into the primary would transform the party by animating many conservatives and disaffected voters who were disinterested in Bush's more mainstream Republicanism.

After losing the Iowa caucuses and the New Hampshire and South Carolina primaries, Bush exited the race, and Kinzinger suddenly needed to find a new candidate to support.

Turned off by Trump's candidacy, Kinzinger eventually got behind Florida Sen. Marco Rubio, who since the 2010 midterm elections had been touted as a future leader of the party.

But in Kinzinger's newly-released book, "Renegade," he revealed that upon reflection, he should have been "worried" at the seamless manner in which he corresponded with Rubio about endorsing the Floridian's presidential campaign.

"With Bush dropping out, my best anyone-but-Trump option was Rubio," the former lawmaker wrote. "After we texted a few times, I decided to back him publicly and went to meet his campaign people in Washington."

"In retrospect, I should have been worried that it had been so easy to text with Marco," he continued. "No one running for president should be that available."

Kinzinger, who was enthusiastic about Bush's candidacy, describing the ex-governor as "a thoughtful person," went on to detail how Rubio's candidacy at the time was less grounded in longstanding campaigning norms but moreso in the media.

"The press had been reporting that he was rarely seen in the early primary states, had almost no local operatives in these states, and that his team had concluded that traditional campaigning was not a good investment. Better to focus on press appearances and social media," Kinzinger wrote of Rubio's presidential operation.

"However, press reports and social media attention come only after you distinguish yourself from the pack. To do that, you must get in front of people," he added.

Trump's campaign continued to gain steam, and by the time the GOP primary reached Florida, Rubio had not been to blunt the New York businessman's momentum.

After Trump trounced Rubio in his own home state, the senator suspended his presidential campaign.

During Trump's presidency, Kinzinger's wariness with the GOP leader never went away as he sought to navigate a changing party that was becoming more and more committed to Trumpism.

Kinzinger eventually backed Trump's impeachment for "incitement of insurrection" for the then-president's role on January 6, 2021, and also served on the House committee investigating the riot at the US Capitol.

He left office in January 2023.