Reports over the weekend

indicate that Florida U.S. Sen. Marco Rubio is expected to announce on April 13 that he will run for president in 2016. However, a number of obstacles will likely face the first-term senator.

National Journal reports that although Rubio has low polling numbers, it is actually a familiar role for him:

"This time six years ago, Rubio was an afterthought in a US Senate race that appeared destined to belong to Gov. Charlie Crist and the GOP establishment. It didn't take long for Rubio to turn the race upside down, using his family's immigrant story and his exceptional oratory skills to become a favorite of the conservative base - in Florida and nationally."

Rubio was not an unknown or obscure political figure in Florida. He served as a state legislator for nine years, two of which he served as speaker of the House.

Challenging Crist in the Senate primary could have proved a battle, but Crist's early decision to support President Obama's economic stimulus plan was unacceptable within his party. The outcry was such that Crist defected to the Democrats and Rubio, as the alternative to Crist, claimed the nomination.

In a field with many more candidates, however, this volte-face will be harder to turn.

By making immigration reform a priority in 2013, Rubio experienced a backlash from the Republican base that supported him in 2010. In the Conservative Political Action Conference (CPAC) straw poll, which tends to measure conservative and grassroots support, Rubio fell from second place with 23 percent in 2013 to less than four percent in 2015.

The Real Clear Politics polling average in Florida has Rubio at only 13.7 percent -- in his home state. He trails former Florida Governor Jeb Bush, Wisconsin Governor Scott Walker, and is only slightly ahead of neurosurgeon Ben Carson.

Despite deviations from conservative orthodoxy, John McCain and Mitt Romney were still able to win the presidential nomination. However, they faced few establishment rivals and adhered to a hawkish foreign policy. Rubio, who generally identifies as a conservative, could face a tougher road than those predecessors.

Although the GOP appears to remain hawkish, Rubio could find himself on the wrong side of issues as they concern Republican primary voters. As an early supporter of the 2011 intervention in Libya, Rubio would have to defend himself to conservative voters about why he was on the same side as possible Democratic nominee Hillary Clinton.

Additionally, the GOP field is also likely to see other hawks such as Peter King and Lindsey Graham run. Alongside them could be governors Scott Walker and Chris Christie, who have also fashioned themselves on hawkish lines. Combined with fewer debates than in recent cycles, this could inhibit Rubio's ability to stand out from the crowd and make his voice heard.

Rubio's electability might also be overestimated. When he won in 2010 with 2.6 million votes, slightly less than 50 percent of the voting population turned out to participate in the election. It was the second-lowest voter turnout in Florida in 50 years.

Two years later, in 2012, when turnout was much higher, Republican Connie Mack finished with 3.4 million and was still more than 1 million votes shy of Sen. Bill Nelson. For a closer comparison, in the previous midterm Senate election in 2006, Nelson earned 2.8 million, about 200,000 more than Rubio in 2010.

The 2016 field is far from complete and while Marco Rubio is likely to have backers, he also faces many question marks.