[WASHINGTON] US Democrats have their 2016 presidential frontrunner in Hillary Clinton, but the Republican field remains wide open - and it got even wider on Monday, with first-term Senator Marco Rubio joining the race.
Mr Rubio - a Florida lawmaker and son of immigrants from Cuba who is equally at ease discussing foreign policy, deficit reduction, his family's compelling narrative or hip-hop music - joins two other Republican first-term senators who are already running: Ted Cruz of Texas, who like Rubio is Cuban-American, and libertarian-leaning Rand Paul from Kentucky.
While Mrs Clinton has few serious challengers from within her party - Vice President Joe Biden and former Maryland governor Martin O'Malley have expressed interest but little else - several more Republicans are considering jumping into the fray, including Wisconsin Governor Scott Walker and former Texas governor Rick Perry.
Should Mr Bush, the son and brother of two former presidents, enter the race as expected, his duel against fellow Floridian Rubio could be one of the more compelling narratives of the 2016 campaign
CLOSING THE GENERATION GAP
Mr Rubio, who often casts his personal arc as the embodiment of the "American Dream", wants to take voters beyond the dynastic Bush-Clinton dynamic that has ruled US politics for much of the last quarter century.
He and his team have telegraphed some of Mr Rubio's themes for the Monday night event in Miami, notably that he is the candidate for a "new American century."
Youthful, charismatic, and articulate on several issues, Mr Rubio hopes to transcend the Republican Party's reputation for difficulty in connecting with young, Hispanic or African-American voters.
Mr Rubio, who is hawkish on foreign policy, is a Tea Party favourite with potential to draw conservative votes.
But he angered core conservatives two years ago when he helped craft a historic immigration reform bill that would have provided pathways to citizenship for millions of undocumented workers, a plan he has subsequently backed away from.
HILLARY HITS THE ROAD
Former secretary of state Clinton meanwhile ended years of speculation on Sunday when she finally announced what everyone already knew: her intention to join the race to succeed Barack Obama in the White House and give Democrats a third straight presidential term for the first time in more than half a century.
Mrs Clinton hit the campaign trail Sunday, striking a note of soft humility with her pledge to champion "everyday Americans" - a departure from her hard-as-nails approach in 2008, when she lost her party's nomination to Obama.
Crowding into a minivan, she drove from her New York headquarters toward the crucial midwestern state of Iowa, where she will hold small roundtables with middle-class voters, students and local and state officials beginning Tuesday.
A few hours into the surprise 1,600km journey, the 67-year-old former senator and onetime first lady tweeted a picture of herself meeting a family at a Pennsylvania gas station.
"This was her idea and she has been really excited about it. We've been driving for a good part of today," close Clinton aide Huma Abedin said on a conference call from the road late Sunday.
Mrs Clinton's first major rally and the speech that kicks off her campaign is not expected until May.
"We can't take anything for granted," added Mrs Clinton campaign manager Robby Mook.
"We'll have to fight really hard for every single vote, and that obviously starts in the primaries."
While Mrs Clinton aims to break what she calls the final "glass ceiling" and become the nation's first female commander-in-chief, her Republican rivals want to reverse course from what will be eight years of Obama policies they say have made America weaker and economically stagnant.