The first-in-the-nation presidential voting contest begins tonight in Iowa at 7 p.m. CT.

After months of speculation, debate and retail politicking on behalf of the GOP candidates seeking their party's nomination for president, the big day has finally arrived.

It has not been an easy road; a great deal of time and money was spent leading up to this day. ABC News breaks down some of the numbers.

As of tonight's caucus, the six leading GOP candidates have spent 354 days in the Hawkeye State, according to calculations from the Des Moines Register, and traveled more than 23,000 miles.

In addition to their time, candidates spent big money in Iowa. They or the super PACs supporting them have spent $12.5 million and counting on television ads in the state, according to firms that track advertisements. That number breaks down to $104 spent per Republican caucus-goer on ads, based off of the estimated 120,000 caucus-goers who turned out in 2008.

Candidates have taken different approaches in the state. Frontrunner Mitt Romney logged 771 miles in Iowa in just three days - beginning Jan. 1 and ending today. Interestingly enough, the former Massachusetts governor has spent the least amount of days campaigning in the state -  just 18, not including this evening's voting contest.

Michele Bachmann, who is trailing in the polls, visited all 99 counties in the state in an 11-day span, during which she traveled roughly 6,200 miles and distributed 5,000 lawn signs.

By his own estimation, Rick Santorum has held more than 370 town hall meetings and the attendance levels have ranged from 1 person to 300. Santorum, who has been  surging towards the top of the pack recently, has clocked the most days in the state leading up to tonight's event - 104.

After months of hard work, the candidates will make their final pleas today. And perhaps the die has not yet been cast; the latest poll from the Des Moines Register reported that 41 percent of Iowans said they could still be persuaded to change their support from their current first choice.

ABC News' Chris Good, Emily Friedman, Russell Goldman, Arlette Saenz, Jason Volack and Shushannah Walshe contributed to this report.