Republican race

Marco Rubio (pictured above) did not waste any time taking on Hillary Clinton, the widely assumed Democratic candidate-to-beat in the presidential election 2016. Not even ten minutes into his announcement speech, the 43-year-old Rubio blasted 67-year-old Clinton who had declared her bid the previous day, as a leader from yesterday, and framed the presidential race as a "generational choice" about the future of the country.

With his attack against Hillary Clinton during his own presidential candidacy announcement, Rubio's political career comes full circle in a way. As highlighted in a telling #link:http://www.washingtonpost.com/blogs/the-fix/wp/2015/04/13/marco-rubios-been-battling-clintons-since-1996-heres-photographic-proof/?tid=sm_tw:black-and-white picture# by the Washington Post, he has been fighting the Clintons for close to two decades now.

Back in 1996 as a college student, Rubio wrote campaign placards for Republican candidate Bob Dole's failed bid to oust President Bill Clinton. Now, almost twenty years later, Florida Senator Rubio is trying to prevent another Clinton presidency, only this time it is not Bill, but Hillary that is running.

Young guns

There's not much daylight between Rubio's approach to Clinton and that of another conservative young gun, Ted Cruz, the first Republican candidate to announce his presidential bid. In many ways Cruz, a 44-year Senator from Texas, seems a brainier and more right-wing incarnation of his Congressional colleague.

Rubio holds degrees from Florida universities, Cruz attended Princeton and Harvard. And even though both are closely aligned with the tea party faction of the Republican Party, Cruz appears to have a stronger ideological bent.

He is so far probably best-known for reading the Dr. Seuss' children's classic "Green Eggs and Ham" more than five hours into a symbolic filibuster speech in Congress to try to stop President Obama's health care reform, reviled by Republicans.

Cruz and Rubio have in common that they both hail from key Southern states and have Hispanic roots. "This is an interesting feature of the field," said Julia Azari, a political scientist at Marquette University, particularly for the Republican Party, which has been struggling to attract Hispanic voters in recent presidential elections due to its opposition to immigration reform.

Uncertain boost

"The other obstacle with Latino voters is economic, of course", adds Azari. "In this regard, we might expect them to behave like white voters - wealthier Latinos will tend toward the Republicans, while those with fewer resources will tend toward the Democrats."

Philip Klinkner, an American politics scholar at Hamilton College, is not convinced their Hispanic background will necessarily give Rubio and Cruz a boost with that voter segment.

"Cruz does not stress his Latino heritage to the same extent as Rubio does and I doubt if it will have much impact on his candidacy one way or another," said Klinkner. "Rubio is helped that he might potentially help Republicans reach out to Latino voters, but so far that's mostly speculation and the polls suggest that he's not that popular among non-Cuban Latinos."

Libertarian voice

Rand Paul, the third declared Republican candidate so far, is a Senator like Cruz and Rubio with a strong disdain for the Clintons and for what all of them consider an oversized federal government. But that's where the easy similarities end. Because, unlike his Senate colleagues, Paul, a Libertarian, wants the US to not play a stronger role on the world stage, but instead has repeatedly criticized what he views as America's oversized global military footprint.

Paul also wants to rein in the NSA and other US intelligence services because he thinks they intrude unduly upon the civil liberties of American citizens. He has also called for a reform of the sentences for drug offenses and an overhaul of the US criminal justice system, which has the highest incarceration rate in the world.

While, politically, Paul does not have much in common with Cruz and Rubio, the trio to first declare their presidential ambitions will likely share the same fate: They probably won't win the Republican nomination.

Bush and Walker

"Jeb Bush is the clear front-runner - I think absent an unexpected surge - in donations, or maybe in an early primary - or a major misstep from Bush - he will get the nod," predicted Azari.

"Bush and Walker are the two strongest candidates at this point," said Klinkner, refering to Scott Walker, the governor of Wisconson.

"Rubio might emerge as a contender, but the rest of the announced ,or likely to announce, candidates have very little chance of winning the nomination."

Bush, the former Florida governor and brother of President George W. Bush, has not officially declared his candidacy, but is widely viewed to be for the Republican primary what Hillary Clinton is on the Democratic side: The candidate to beat.

Bush has deep coffers, political experience, the support of the party's establishment and unlike Paul, Cruz and Rubio is considered centrist enough to not alienate mainstream voters in a presidential campaign against a Clinton or another Democratic contender. His challenge will be to win over the party's conservative wing to get the nomination without leaning too far to the right to hurt his chances in a national election.

Union buster

Governor Walker has not declared his candidacy, but is doing very well in opinion polls. Politically, Walker, who is currently in Germany on a trade mission, positioned himself clearly to the right of the Republican Party.

He garnered national attention – and the admiration of the tea party faction – when he curbed the collective bargaining rights for most public employees in his state. Walker's controversial move led to a recall election, which he won, making him the only governor in the US to survive such a vote.

Notwithstanding Bush and Walker's strong showing in the early stages of the Republican primary, compared to the Democratic race the conservative nomination appears wide-open. Unless Vice President Joe Biden or Senator Elizabeth Warren decide to run, Hillary Clinton may face no serious challenge for her party's nomination. Things look very different on the Republican side. More than ten candidates are still mulling whether to join the race.