Hey, I have a little background on this question!

There was some criticism of Hughes and the Republicans for nominating a Supreme Court Justice, though it was surprisingly mild, and mostly before he received the nomination. An article in the May 4, 1916, edition of the Wallace Miner newspaper in Wallace, Idaho, probably sums it up best:

"The opposition to the nomination of Justice Highes has never been based upon personal grounds, for he is universally recognized as a man in every respect admirably equipped for the presidency. The opposition has been based solely upon the feeling that prevails among thoughtful [R]epublicans that the [S]upreme [C]ourt should be kept free from party strife, and a fear that once the precedent is established, even though the honor is unsought, the time may come when other justices might seek the presidency and thus destroy the splendid prestige the supreme bench has always maintained on account of its freedom from the rancor of partisan politics."

State Senator from Pennsylvania, John S. Weller, a Republican-affiliated Progressive, echoed these sentiments in an article in the May 25, 1916, edition of the New York World:

"The Supreme Court is generally regarded as the highest court in the world. To encourage members to entertain hope of the Presidency would be to cast an influence in that court that might be reflected in its opinions."

In the March 19, 1916, edition of the Washington, D.C., Evening Star, a reporter recounted an interview he'd had with Hughes back in 1910, when he had resigned the Governorship of New York to take the Supreme Court seat. In retrospect, it made Hughes either sound hypocritical, or as having secret Presidential ambitions all along:

"But will Hughes accept it [the nomination]? In thinking this over, my mind goes back to a talk with Governor Hughes in the Albany executive chamber in the early summer of 1910...His usefulness as Governor, he said, was over; he had served four years, and two terms was about as fixed a tradition for the New York governorship as two terms for the Presidency. He had only one thing before him—a return to the practice of law. This was distasteful, for several reasons. He would be under the suspicion of coining his career as an investigator and Governor into money—Mr. Hughes had no illusions on the fact that his earnings would be very large.

"Again,—what was even more distasteful,—his every word and act would be interpreted as a bid for the Presidency. In going on the Supreme Court bench, however, he as definitely removed himself from political preferment as by going into a monastery.

"'Don't be so sure of that,' I interjected at this point.

"The Governor wheeled around in a flash. 'You mustn't say that!' he exclaimed emphatically. My remark had evidently not been a pleasing one.

"But, in thinking of the chances that Hughes might run, this little experience naturally comes to mind. He did not intend to enter politics when he went on the bench: but the present situation certainly has its temptations."

After receiving the nomination, the attacks on this point were made by the Democrats, as exemplified by an editorial from August 1, 1916, published in William Jennings Bryan's The Commoner newspaper in Lincoln, Nebraska:

"As no justice of the [S]upreme [C]ourt was ever nominated for the president before, Mr. Hughes is setting a new precedent. He is showing us how, in his opinion, experience on the supreme bench should fit one for the political arena. He has answered one of the [D]emocratic arguments—the only one he has attempted to. The [D]emocrats protested against a nominee being taken from the [S]upreme [C]ourt. After reading Mr. Hughes's speeches, the counrty will be convinced that his partisan bias is better suited to a political campaign than to a position which requires a judicial temperament."

Hughes attempted to address the criticism from the start. Before the Republican National Convention, he had repeatedly denied being interested in the nomination, though he was aware that there were party leaders attempting to draft him (and he never made a statement that he would not serve if nominated). Upon accepting the nomination, he said that his acceptance was out of a sense of duty and patriotism:

"I have not desired the nomination. I have wished to remain on the bench. But in this critical period of our national history I recognize that it is your right to summon and that it is my paramount duty to respond. You speak at a time of national exigency transcending merely partisan consideration.

"You voice the demand for a dominant, thorough-going Americanism, with firm, protective upbuilding policies essential to our peace and security, and to that call, in this crisis, I cannot fail to answer with the pledge of all that is in me to the service of our country. Therefore I accept the nomination."

A couple days later, he reiterated this position in a statement to the press:

"Mr. Hughes received newspaper men during the forenoon, but declined to discuss his plans. He was asked how it felt to be 'drafted for the biggest job in the world?'

"'I can only say, he replied, 'there are certain circumstances under which a matter of duty is supremely clear and which leaves no ground for hesitancy in this case. There was no question in this situation as to what I should do. I did it, and in my announcement to the people I endeavored to make my attitude clear.'"

That all said, it actually played a very minor role in the campaign. The bigger issue that was used as a punching bag by the Democrats was that Hughes was a desperation candidate by the Republicans. There were deep divisions within the party, dating back four years to the split between the "Old Guard" "Bourbon Republicans" of Taft, and the "Bull Moose" "Progressives" of Theodore Roosevelt. Hughes was a compromise, because he was just acceptable enough to the Progressives that they wouldn't nominate their own third-party candidate. However, even that wasn't a sure thing. As Hughes' name started popping up around March 1916, the Progressives planned to fight his nomination. Minnesota's Labor World newspaper, for instance, published a piece in their April 1st issue giving a list of reasons why they predicted Hughes' nomination wouldn't happen. #1: "Roosevelt does not like Hughes and would not support him." #2: "Hughes does not like Roosevelt and would not accept the latter's for-God-and-country platform." #3 was actually a reference to Hughes' Supreme Court seat, but only in the sense that they thought Hughes would never want to leave a lifetime position for the possibility of a four-year position that he very well might lose. None of the reasons were about judicial independence.

cont'd...