Florida senator Marco Rubio joined his Republican Party’s presidential primary race on Monday when he announced his candidacy to donors in a news call. He was due to kick off his campaign with a speech in Miami later in the day.

The one-term senator seems a long-shot candidate. Although he was hailed as something of a conservative wonderkid when he first won election in 2010, his star has faded. From a clumsy State of the Union rebuttal in 2013 to the defeat of a comprehensive immigration reform law he sponsored that same year, the Cuban American has at times seemed ill-prepared for national politics.

His heritage might help Republicans win more support from Hispanics than they did in the last presidential election when Mitt Romney’s promise to make life so tough for illegal aliens in America that they would “self-deport” led to the party winning just 27 percent of the Hispanic vote.

Rubio has lately played down his support for immigration reform but still backs legal status for the children of migrants. Like many whose families came to the United States legally, he opposes a general amnesty.

Rubio’s social conservatism should appeal to a segment of the Republican primary electorate. He would restrict access to abortion, opposes gay marriage, opposed letting gays serve openly in the military and once described letting gay foster parents raise children as an unwelcome “social experiment.”

Such rhetoric is less popular in the country at large. For a growing number of Americans, gay rights are a proxy issue for liberal values.

It is unclear what niche Rubio could carve out for himself in what looks to be a crowded primary field. His fellow senator from Texas, Ted Cruz, is more likely to appeal to evangelicals and tea party voters. His fellow Floridan, Jeb Bush, is a more plausible advocate of immigration and school reform.

Since his immigration proposal was defeated, Rubio has focused on foreign policy issues but yet to demonstrate a firm grasp of them.

Rubio supported the 2011 intervention in Libya but then turned round on President Barack Obama, insisting that a wholehearted commitment of American forces would have prevented a worse civil war. He later took the president to task for ending half a century of Cuban isolation, characterizing his cancelation of such an obviously failed policy as “part of a long record of coddling dictators and tyrants.” And he incredulously claimed that the president didn’t want to defeat Islamic State jihadists in Iraq and Syria because he was afraid to “upset” Iran — even though Iran is fighting the same militants.