Ted Cruz and Marco Rubio are riding a wave of momentum after strong finishes in Iowa. Donald Trump maintains a double-digit lead over his Republican rivals, but Rubio has experienced the largest surge, according to an NBC News/SurveyMonkey tracking poll released Tuesday. The billionaire businessman has 35 percent support nationally among Republicans and Republican-leaning voters. Ted Cruz, who won the Iowa caucuses last week, has 20 percent support, followed by Rubio in third with 17 percent support. Ben Carson is at 7 percent, and the rest of the field is at 3 percent or less. While Trump still leads by...