U.S. Senator Irvine Lenroot (R-WI), Vice President (1921-1923), President 1923-1933).
Lenroot was selected as running mate to Warren Harding in 1920 to placate the Progressive wing of the Republican Party. Lenroot succeeded as President when Harding died in late 1923. Lenroot's immediate move to prosecute Fall, Doheny, and Sinclair for the Teapot Dome bribery won him plaudits and helped the GOP shed the taint of the scandal.
He was re-elected in 1924, by an even bigger landslide than Harding in 1920. (Lenroot being a Progressive from Wisconsin, there was no LaFollette candidacy, and the Democrats were as divided as in OTL.)
In his first full term, Lenroot decided to use the massive Republican majorities in Congress to tackle a problem Harding, Taft, and Roosevelt had all largely ignored: the white supremacist regime in the South. He started by denouncing lynching as a horrific scandal, a massive stain on the character of the United States, and one that must be removed. Congress passed an anti-lynching bill in 1926, which empowered Federal investigation and prosecution of lynchers. It was supported by not only Repblicans, but many Northern Democrats (especially Catholics who disliked the Klan and Jews who saw lynching as a parallel to the pogroms of Russia).
Lenroot's campaign split the South. While a core of die-hards tried to resist the anti-lynching program, another large group preferred to co-operate - to get rid of lynching (which was in decline, anyway) and salvage the image of the "New South". Ultimately, the "New Southerners" won out, as the die-hards were crushed by Federal power. (The new FBI and its brilliant young Director, J. Edgar Hoover, won fame for daring undercover work, which included a number of black Agents.)
Lenroot was easily re-elected in 1928. In 1931, as what seemed a necessary step to break lyncher resistance, he pushed through the Voting Rights Act, which restored the suffrage of blacks in the South. (The lynchers relied on their control of local government and law enforcement; enfranchising blacks gave them control of many towns, cities, and counties, breaking the "lily-white wall".) The lynchers tried to resist, but the New Southerners found it more advisable to bend, rather than be broken. They followed the example of Memphis "Boss" E.H. Crump, co-opting black leaders with a modest share of patronage in return for black votes. But black voting systematically undermined the entire basis of white supremacy and Jim Crow. Also. the NAACP used the 14th Amendment to force white-controlled local governments to live up to the "equal" part of "separate and equal"; they won hundreds of law suits forcing school districts to provided equal pay to black teachers. [As in the OTL 1940s.] By the 1950s, activists were winning desegregation of public accommodations such as trains, buses, and government offices. In the 1960s, hotels and restaurants followed, and the Supreme Court struck down the real estate "covenants" which enforced residential segregation.
Lenroot had also addressed another national problem earlier. As a Progressive, he had supported establishing the Federal Reserve Bank; now he pushed for a system of deposit insurance. The Federal Deposit Protection Act passed in early 1930. The Act included provision for a federally-guaranteed bond issue to provide initial funding, which proved to be very useful, when a number of banks failed as a consequence of the stock market crash of the previous fall. The depositors were all protected, which almost certainly avoided runs on many other banks in difficulties, and a cascade of bank failures that could have plunged the country into a severe economic crisis.
Instead, the panic died out almost at once. There was a downturn, with unemployment spiking up to over 13% in mid-1931. But recovery began almost at immediately, and by mid-1932 unemployment was back down under 8%. Hardly anyone realized it at the time, but the U.S. had avoided an economic catastrophe. It was not till 1958 that Paul Samuelson in retrospect showed what Lenroot had achieved.
When this was added to his leadership in civil rights, Lenroot was recognized as one of the greatest U.S. Presidents.
(And I'm extremely embarassed to realize that I forgot this is a Pre-1900 thread. Oh well.)