When we endorsed Rubio in his U.S. Senate bid in 2010, we applauded him for being "willing to confront head on the massive budget deficits that threaten to undermine American prosperity, prestige and power." He's still willing to do so, having proposed in his current campaign politically risky but fiscally responsible changes to sustain Social Security and Medicare for future generations. Trump, by contrast, has ruled out changes in either program.