Sen. John McCain (R-Ariz.) says people shouldn't underestimate President Obama as he heads into his sixth year in the White House.
He discounted Obama's low approval ratings and said a sitting president always has influence.
"We all wear thin with the American people after a while," McCain told the Associated Press.
McCain has had his up-and-downs in his relationship with Obama, his foe during the 2008 presidential campaign.
He met with Obama this year to discuss immigration reform, but was a vocal critic of the president's foreign policy moves in Syria and elsewhere.
Democrats and Obama plan to make immigration reform a top priority in 2014, and are pushing House Republicans to take up legislation.