WASHINGTON — President Barack Obama’s nominee to be the first U.S ambassador to Cuba in more than 50 years faced immediate opposition from GOP senators Wednesday, casting serious doubt on the long-shot attempt to get Senate confirmation of Jeffrey DeLaurentis.

Sen. Lindsey Graham, R-S.C., called Obama’s Tuesday evening nomination of DeLaurentis, who already serves as the chief of mission at the U.S. Embassy in Havana, “completely symbolic” and said Senate confirmation “won’t happen.”

The nomination, which came amid furious negotiations to avoid a government shutdown just days before the Senate breaks for campaign season, will likely not be debated until after the November elections.

“During the lame duck session there would be a window of opportunity depending on what happens in November,” said Ted Piccone, a senior fellow at the Brookings Institution. “Senate confirmations in the case of many ambassadorial appointments, particularly in controversial countries, is like making sausage, it’s not pretty. It’s a question of bargaining and tradeoffs and this starts the process of negotiations.”

If confirmed, DeLaurentis would have an elevated status but the change would be mainly political, according to Piccone. The nomination also served to quell behind-the-scenes bids of other candidates who were lobbying for a future ambassadorship, he said.

Florida Republican Sen. Marco Rubio, the son of Cuban immigrants and a critic of the Obama administration’s diplomatic relations with Cuba, called the nomination a “last-ditch legacy project” in a sharply worded statement on Tuesday.

“This nomination should go nowhere until the Castro regime makes significant and irreversible progress in the areas of human rights and political freedom for the Cuban people, and until longstanding concerns about the Cuban regime’s theft of property and crimes against American citizens are addressed,” he said.

While many Republicans oppose holding confirmation hearings for DeLaurentis, under Senate rules it only takes one to block the proceedings. Last year, Rubio blocked Roberta Jacobson’s confirmation as U.S. ambassador to Mexico until this April due to her involvement in negotiations with Cuba.

Obama called the nomination a “common sense step forward” toward more normalized relations with Cuba.

“Having an ambassador will make it easier to advocate for our interests, and will deepen our understanding even when we know that we will continue to have differences with the Cuban government,” Obama said at the White House announcement.

Arizona Republican Jeff Flake, a key Obama ally on Cuba policy, broke with the majority of his party tweeting: “Americans traveling & doing business in #Cuba will be well-served by the prompt confirmation of Jeff DeLaurentis to serve as US ambassador.”

The U.S. severed diplomatic ties with Cuba in 1961 and maintained a policy of diplomatic isolation until Obama announced a rapprochement in 2014 that lifted some economic sanctions, eased travel between the countries and reopened embassies in each other’s capitals.

In 2011 DeLaurentis, a career member of the Senior Foreign Service, was confirmed by voice vote in the Senate to serve as a U.S. representative to the United Nations with the rank of ambassador.