Mitt Romney’s biggest problem was staring him right in the face all along: the overwhelmingly white crowds that greeted him at parks, manufacturing plants, airport hangars and other stops on the campaign trail.

While the Republican nominee campaigned almost exclusively among white voters — whose share of the electorate has been shrinking for decades — President Barack Obama was rebuilding a dynamic coalition of young voters, women, African-Americans, Asians and Hispanics, the country’s fastest growing demographic.

Obama captured 71 percent of the Hispanic vote, helping him lock down key swing states like Colorado, Nevada and Florida. Less noticed was the 73 percent support Obama drew from Asian-Americans, an emerging force in states such as Virginia, an 11 percent improvement from 2008.

Romney got the largest share of the white vote for a Republican since Ronald Reagan in 1984 and still lost.

The 2012 election has forced the GOP to the edge of a demographic cliff. Unless something is done to effectively end the decades-old Southern Strategy of appealing mainly to white voters, Republicans face an uncertain future.

“We have to accept America as it is today and not America as Ward Cleaver saw it,” said GOP strategist John Weaver. “We’re two or three elections away from Texas becoming a swing state,” he added, referring to the reliably Republican state’s rapidly growing Hispanic population.

Whites still make up the largest voting bloc, but the group continues to slide, to 72 percent of the electorate from 74 percent four years ago and 77 percent in 2004. Meanwhile, Hispanics, Asians and African-Americans all boosted their share of the electorate. In Florida, there are 300,000 more Hispanic voters today than in 2008, and 150,000 more black and Caribbean-American voters.

All told, Obama captured 80 percent of the nonwhite vote. It made up for his slide among white voters, who favored Romney by 20 percentage points. Voters age 18 to 29 also grew in numbers, and Obama again won them handily.

The Republican Party finds itself not only behind the demographic curve but out of step on issues gaining national acceptance, like same-sex marriage and immigration reform.

On Tuesday, 65 percent of voters nationally said they supported a pathway to citizenship for undocumented residents, something Republicans have largely dismissed as amnesty. Maryland, Maine and Washington state became the first to approve gay marriage by popular vote, while Minnesota voters rejected a proposed constitutional amendment to ban same-sex marriage.

“Republicans are a Mad Men party in a Modern Family America,” Republican consultant Matthew Dowd said on Twitter after the election. “They need to adapt to 21st-century country and demography.”

The increasingly polarized electorate raises questions about where the country stands four years after electing the first black president. During the campaign, Romney and his supporters frequently suggested the president didn’t understand American values.

Conservative talk show host Bill O’Reilly lamented on Fox News Tuesday night that Obama was headed to victory “because it’s not a traditional America anymore. The white establishment is the minority.” He suggested, as Romney did during the campaign, that Obama’s backers are in search of government handouts.