One way to answer this question is to look forward to the 1916 election. TR and the Progressives loomed large over the Republican National Convention in 1916, and the party knew that they would be forced to nominate someone that was both palatable to TR and that could unite the party’s warring factions. TR refused to support several people seen as contenders, including Republican Senator from Ohio Warren G. Harding, who would later be nominated and win the 1920 presidential election. Oscar S. Straus, former Secretary of Commerce and Labor under TR said, "There has never been a party in this country which has held fewer offices and has had a more distinct and decided influence upon the life of the country in elevating it to a higher plane of thought and action than has been performed by the Progressive Party. This party has been kept alive for four years and has come to Chicago with the freshness of youth and with a power and determination which mean that it can never be beaten." (New York Times, “Hughes Movement Gains Strength,” June 7, 1916.)

Charles Evan Hughes and TR had a long history together, especially thanks to TR’s encouragement that Hughes run for Governor of New York for two terms. Still, TR was not especially pleased with the nomination of Hughes, especially due to some previous political disputes, but it seemed that Hughes was the only one popular enough to win. TR declined the Progressive party’s nomination and supported Hughes, in no small part because he was very invested in making sure Woodrow Wilson was defeated.

The Progressive Party itself dissolved without Roosevelt’s leadership, and the majority of its members joined the Republican party (a few did join the Democrats), and brought with them their ideas. Although in many aspects it remained unchanged – such as in the promotion of protective tariffs - the Republican platform in 1916 had certainly “progressed” on several fronts, the party having been influenced both by a need to court voters and to heal the divide. The 1912 platform, for example, included no mention of women’s suffrage, but the 1916 platform supported it as a state-level decision. Labor laws are barely present in the 1912 platform, but they have their own section in 1916. The Republican platform of 1916 supports federal labor laws, in particular workmen’s compensation laws, and the collection of data about incidents in the workplace to help support the development of such laws. The 1916 platform also calls for the regulation of transportation systems, which had become “essentially national,” by an amendment to the Constitution if necessary. (Texts compared on the American Presidency Project website, https://www.presidency.ucsb.edu/)

Thanks to the absorption of the Progressive Party into the Republican Party, the threat of the vote being split as it had in 1912 became slim. Indeed, the incumbent President Woodrow Wilson won the 1916 election, but not by an especially large margin – 49% of the popular vote compared to Hughes’ 46%. Hughes made a few mistakes in his campaign that sunk him, most notably attacking Wilson’s pro-labor policies (seemingly in spite of the Republican platform, losing him voters on both sides) and snubbing Republican Governor Hiram Johnson of California. Without those major missteps, Hughes, a respected statesman both before and well after this election, may very well have defeated Wilson and secured further influence for the Republican party.