Sen. Jeff Flake (R-Ariz.) told CNN's "State of the Union" that he's "very concerned" about Republicans' chances in the 2020 presidential election — both in Arizona and in suburbs around the country. Discussing his home state, which just flipped his Senate seat to Democrat Kyrsten Sinema, Flake said, "You cannot run as someone who is tied at the hip with the president and win statewide."

Go deeper: The warning signs for Republicans ahead of 2020