Who is Bob Corker? A closer look at the Tennessee senator after tiff with President Donald Trump

If Tennessee Senator Bob Corker thought retirement might be the easy way out of Washington, he may have to reconsider his rather surprising decision.

The two-term Republican announced last week he would not seek a third term, which means eventually giving up his coveted chairmanship of the Senate Foreign Relations Committee.

Then came the tweetstorm.

President Donald Trump, who reportedly once considered Corker as a possible running mate or Secretary of State, lashed out at Corker on Twitter, saying "Senator Bob Corker 'begged' me to endorse him for re-election in Tennessee. I said 'NO' and he dropped out (said he could not win without... ..my endorsement). He also wanted to be Secretary of State, I said 'NO THANKS.' He is also largely responsible for the horrendous Iran Deal! Hence, I would fully expect Corker to be a negative voice and stand in the way of our great agenda. Didn't have the guts to run!"

Corker replied, "It's a shame the White House has become an adult day care center. Someone obviously missed their shift this morning."

So who IS Bob Corker? FOX 5's Jim Lokay spoke with Jamil Jaffer, who worked alongside Corker as a senior advisor to the Senate Foreign Relations Committee, on "The Final 5."

Jaffer called his former boss "smart," and derided the president's claims that he was responsible for the Iran nuclear deal, saying the senator actually mobilized a bipartisan effort against the accord - which came into being only after Democrats blocked a procedural motion in 2015.

Corker, who will continue to serve through early 2019, is seen by many to wield considerable power, even as a "lame duck."

In the video player above, watch FOX 5's Jim Lokay's interview with Jamil Jaffer.