Theodore Roosevelt is widely regarded as the first modern President of the United States. The stature and influence that the office has today began to develop with TR. Throughout the second half of the 1800s, Congress had been the most powerful branch of government. And although the presidency began to amass more power during the 1880s, Roosevelt completed the transition to a strong, effective executive. He made the President, rather than the political parties or Congress, the center of American politics. Roosevelt did this through the force of his personality and through aggressive executive action.