What would the world be like if President McKinley was never assassinated?

McKinley's death by assassination opened the door to the presidency for Theodore Roosevelt. To begin to think about the ways this changed the office, the country, and America's role in international affairs, it seems sensible to look at what McKinley's successor brought to the fore.
Roosevelt's progressive movement included the Square Deal, which negotiated competing ideologies between labor and business. He sought to federally regulate trusts that he believed to be exploitative and harmful to the general public. On the international scene, Roosevelt sought to balance power while maintaining America's strong foreign policy stance. Building on McKinley's initiative, he welcomed the press into the White House and used it to build his own popularity, changing the way candidates campaigned and managed their presidencies. Roosevelt's influence is observable in the succeeding progressive movements of FDR, Truman, JFK, and Johnson.