President Obama's muscular victories in 2008 and 2012 inflated Democratic egos, giving the party visions of a never-ending string of victories in nationwide presidential races.

Just a few years later, such over-confident prognosticating seems extremely ill-advised.

The 2014 midterm elections were a disaster for the president's party. Republicans picked up nine Senate seats, claiming a majority for the first time in eight years. And House Republicans bolstered their ranks to the party's highest levels since Herbert Hoover was president.

Even worse for Democrats: The apparent loosening of their near-lock on the Electoral College, which actually determines who gets to the White House. In three states that were critical to Obama's wins in 2008 and 2012 — Nevada, Colorado, and Virginia — Republicans showed remarkable resurgence and strength in 2014.

These states were very recently thought to be safely in the Democratic column. Demographics had seriously shifted in recent years, thanks in no small part to influxes of Latino voters, Asian residents, and other swaths of non-whites. Bankable wins here meant Democrats could forgo traditional battlegrounds like Florida and Ohio and still win an Electoral College majority.

The three states are worth 28 electoral votes, out of the 270 needed to win. But add that onto the 242 electoral votes Democratic candidates won in the six presidential races from 1992 to 2012, and they're in the White House, with what seems like an all-but-assured win every four years.

Not so fast! Thanks to the GOP's big comeback in 2014, Republicans have plenty of reasons for optimism as the next White House scrum gets going.

Nevada. The Silver State was long frustratingly out of reach for Democrats. Despite Nevada's unusually influential organized labor movement, conservative-leaning suburbanites in the Las Vegas area and the state's massive northern sector gave Nevada a strong Republican tilt.

That finally changed for Democrats in 2008, after losing two straight Nevada presidential contests with George W. Bush heading the GOP ticket. The national economic collapse hit Nevada's tenuous housing market particularly hard. And party organizers mobilized Nevada's rapidly growing number of Latinos and Asians, many naturalized citizens. The Obama campaign racked up 55 percent of the vote. Four years later, with the desert economy still lagging, Obama prevailed over Mitt Romney, 52 percent to 46 percent.

Just two years later, though, Republicans rallied big time. In 2014 Republicans picked up both chambers of the state legislature. And in one of the biggest surprises of Election Night, freshman Democratic Rep. Steve Horsford lost to Republican challenger Cresent Hardy, a state assemblyman. Republicans also won a hotly contested race for Nevada attorney.

Nevada Republicans clearly have the wind at their backs. And if there's a friendly national political atmosphere come 2016, there's every reason to think the state is back in play for Republicans. That would be huge: Nevada has been carried by the winner in every presidential election since 1912, except for 1976.

The trick will be increasing registration, getting people out to vote, and crucially, appealing to Latinos. There's already reason for optimism on that front. Gov. Brian Sandoval, among the most prominent Republican Latino officeholders, won re-election in a landslide with 70 percent of the vote.

Colorado. Two states to the east, Republicans can celebrate their most successful election in more than a decade. Rep. Cory Gardner knocked off an incumbent Democratic senator, Mark Udall. Colorado Republicans also won back the state Senate majority for the first time since 2004, and made big gains in the state House.

That's a stark turnaround from just two years before. Obama's 2012 win in Colorado — his second straight — was supposed to symbolize the ascendancy of a new Democratic-friendly coalition, with single women and Latino voters at its core. In fact, an exit poll "showed Obama carrying Latinos 75 percent to 23 percent — a big increase over 2008, and a big enough vote to account for all of his popular vote margin in the state," writes The 2014 Almanac of American Politics.

So much for that advantage. That big edge among single women and Latinos proved fleeting and temporal. In 2014, Colorado's turnout of women voters was at its lowest point since 1992, according to ABC News. That despite Udall's repeated attacks on GOP challenger Gardner over issues relating to abortion and contraception.

The Latino vote, too, came up short of what Democratic strategists aimed for. "Latino activists spent months in Colorado organizing voters on behalf of Democratic Senator Mark Udall, a strong supporter of a path to citizenship for undocumented immigrants, against Republican Cory Gardner, who had voted to defund the president's program protecting DREAMers," reports MSNBC. That can't be heartening for Democrats heading into the 2016 presidential race.

Virginia. Leading up to the 2008 election, the Old Dominion had not voted for a Democratic presidential candidate since the 1964 LBJ landslide. But rapidly changing demographics — specifically new liberal-ish voters in suburban northern Virginia — changed the equation.

Virginia was such a high priority for Democrats that Obama made his final 2008 campaign appearance in the far southwest corner of the state, just hours before polls opened. President Obama won Virginia a second time in 2012, cementing its status in the minds of Democratic partisans as safely in their camp.

So imagine their surprise on Election Night 2014 when one of Virginia's two Democratic senators, Mark Warner, narrowly escaped electoral disaster. Warner, a former governor who had been one of Virginia's most popular politicians, was expected to handily win a second term. But Ed Gillespie, a former Republican National Committee chairman, rode a wave of support for GOP candidates nationwide, and almost knocked Warner out of the Senate despite being outspent heavily.

The GOP-friendly midterm results in Virginia, like Colorado and Nevada, won't necessarily hold in the 2016 presidential races. Non-presidential year electorates are famously older, whiter — and more Republican-leaning. But the recent results will, at the very least, keep Democratic campaign operatives up at night. And the eventual Democratic White House nominee will likely have to spend crucial resources on those three states — states that party mandarins once thought they had locked-up.