Question: Marco Rubio presidential campaign, 2016 declared he was running for president approximately three weeks after this fellow republican who has served  as the junior United States Senator from Texas since what year
Sentence (from "Marco Rubio presidential campaign, 2016"): Early polling showed Rubio, who was considered a potential candidate for Vice President by Republican presidential nominee Mitt Romney in 2012, as a frontrunner candidate for the Republican nomination for President of the United States in 2016 since at least the end of the 2012 election.
Relevant evidence: No