McKinley had already won a second term in 1900. It would be someone else in 1904.
Not necessarily. McKinley would have been only 61 in 1904, and probably still popular. Also Ida's health no doubt would have been better had her husband still lived. He might not have gotten the nomination in 1904, but I see no reason he wouldn't have tried.
Great points you make True. McKinley's death caused Ida's health to slip fast. It would have been very interesting to have had Teddy Roosevelt President during WW1. I think the US would have entered WW1 in 1917 or possibly even earlier under the Administration of TR just like it did with Woodrow Wilson.