Senate Republican Leader Mitch McConnell plans to mark his tenure as the chamber's longest-serving party leader with a speech on Tuesday afternoon paying tribute to the previous record holder: former Sen. Mike Mansfield, a Democrat from Montana.

Driving the news: The senior senator from Kentucky, 80, will eclipse Mansfield’s 16 years as party leader on Tuesday. Along the way, McConnell has delighted supporters and bedeviled opponents through crafty procedural maneuvers and — to some critics — brazen power grabs.

• "The greatest honor of my career is representing the Commonwealth of Kentucky in this chamber and fighting for my fellow Kentuckians," McConnell plans to say from the Senate floor.
• "But the second-greatest honor is the trust that my fellow Republican Senators have placed in me to lead our diverse Conference and help them achieve their goals," McConnell will say, according to prepared remarks.

Why it matters: McConnell has stayed in charge of the Senate GOP at a time of intense turmoil in the Republican Party, with powerful populist currents threatening its traditional power structures.

• As minority leader, he warned Democrats not to change the filibuster rules for judicial nominees but then seized on their decision, winning confirmation for three of President Trump's Supreme Court Justices with a simple majority threshold.
• The judicial branch has always been a priority for McConnell and he made his opposition to President Obama's court picks a touchstone of his tenure. Controversially, he refused to allow Obama's selection of then-judge Merrick Garland (now attorney general) to proceed in an election year.

The big picture: Rep. Kevin McCarthy (R-Calif.), who is fighting to become speaker of the House, is the third House GOP leader to work with McConnell since he became leader in 2007.

• Last year, McConnell survived a challenge from Sen. Rick Scott (R-Fla.) and was re-elected party leader, 37-10. He arrived in the Senate after President Reagan's 1984 landslide.
• In June of 2018, McConnell became the longest-serving Republican leader when he surpassed former Sen. Robert Dole (R-Kan.).

Between the lines: McConnell will take stock of previous Senate stalwarts, including Dole, Sen. Robert Taft (R-Ohio), and former President (and former Senate Majority Leader) Lyndon Johnson (D-Texas), commenting on their styles and the secrets of their successes.

• With a wry wink, McConnell will align himself with senators who stayed out of the spotlight — leaders "who preferred to focus on serving their colleagues rather than dominating them,” McConnell will say.
• “And that, Mr. / Madam President, is how Senator Michael Joseph Mansfield of Montana became the longest-serving Senate Leader in American history until this morning."