Washington (CNN) Registered Republicans overtook Democrats in terms of ballots already cast for the first time since voting began in Colorado, according to the latest numbers released Monday.

But even though there are signs that Republicans have late momentum in the Centennial State, they are still behind their 2012 pace, which ultimately wasn't enough for then-Republican nominee Mitt Romney to win.

Colorado is conducting its election almost entirely by mail this year, for the first time in a presidential cycle. Ballots were mailed out to all registered voters starting October 17, and more than 1.8 million Coloradans have already cast their votes by mailing in their ballots or dropping it off at a polling center.

On the eve of the national election, 652,380 Republicans and 645,020 Democrats have cast ballots, according to the Colorado secretary of state. That's a razor-thin Republican lead of 7,360 votes, which is much smaller than the roughly 31,000-ballot edge Republicans had at this point in 2012. So even though Republicans can celebrate taking the lead Monday, they are still underperforming compared to 2012.

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