Republicans went into Tuesday's election fully confident that Mitt Romney would defeat Barack Obama.

In the three months leading up to the election — and even in the dark days of the "47 percent" video leak — virtually every Republican strategist and conservative politico I spoke to was certain that Romney would pull off a victory. Arguments to the contrary were resoundingly dismissed as "a lot of Nate Silver spin."

Instead, the GOP got totally routed Tuesday, losing the White House in an electoral college landslide and squandering what was once a prime opportunity to retake control of the Senate.

It turns out that Republicans had based their projections on two misguided assumptions:

1. That Obama could never win in such a poor economy. Historically, no incumbent since FDR has ever won reelection when the unemployment rate was above 7%, or when the consumer-confidence index was below 95 (it was at 72 in October).

But history only predicts the future until it doesn't anymore. Even as polls continued to show Obama ahead or tied the issue, Republicans kept pointing to grim economic numbers as evidence Romney was going to win the race. Exit polls Tuesday found that while 77% of the electorate has a negative outlook on the economy, more than half of voters, 53%, blame the problems on former President George W. Bush, rather than on Obama.

2. There was no way Obama could mobilize the same turnout he had in 2008. Republicans operated under the assumption that low Democratic enthusiasm and disillusion with Obama would drive down turnout among Latinos, African Americans, and youth voters, the key voting blocs that made up the president's winning 2008 coalition. Romney pollsters predicted that the electorate would be older and whiter in 2012, with whites making up about 76% of the electorate, up from 74% in 2008.

As it turns out, the Romney campaign's polling model was completely wrong. The country is getting more, not less, diverse, and those shifts have been reflected in the electoral turnout for presidential races over the past 20 years. There was no real reason to indicate that 2012 would be any different.

According to exit polls, whites actually made up just 72% of the electorate this year, while Latinos and youth voters upped their share of the electorate by one percentage point each. The African American percentage of the electorate stayed the same.

Karl Rove's meltdown on Fox News Tuesday night illustrated just how shocked Republicans were by this outcome. Rove was convinced that Romney would regain the lead in Ohio with unreported rural white votes, but never anticipated the number of minority voters that would turn out for Obama in the state's urban centers. In Florida, Republicans were similarly floored by the huge Latino and African American turnout for Obama in Tampa.

The flawed assumptions underscore a more fundamental weakness in Republican campaign strategy. The predictions were based off of the vague idea that minority and first-time voters were put under Obama's charismatic spell in 2008, and would retreat from the political landscape now that the "magic" is gone. They failed to account for the Obama campaign's massive, data-driven field operation, designed to get first-time or sporadic voters to the polls, with or without the magic.

In the aftermath of Romney's loss, Republicans have fretted over how the party can appeal to other voting blocs – specifically Latinos. It's a worthwhile exercise, but useless without a mechanism to actually reach out to these voters.

The bottom line is that Republicans got distracted by 'momentum,' cheering crowds, SuperPACS, and yard signs, and ignored the actual purpose of a political campaign: Convincing voters to like you and then getting them to the polls.