DES MOINES - Let the wild rumpus start.

Only three weeks from the Iowa caucuses, the top Republican candidates will square off tonight at a pivotal debate in the state capital. The debate, hosted by ABC News and moderated by Diane Sawyer and George Stephanopoulos, starts at 9pm ET, live from Drake University.

The prime-time debate comes as the GOP race has started to reach a boiling point. With Newt Gingrich surging to the top of the pack, former front-runner Mitt Romney has launched scathing attacks from all sides, from his key surrogates to a political action committee that, while not affiliated with the campaign, is funded by many Romney donors.

The ad accuses Gingrich of "flip flopping" on a slew of issues and claims that Democrats are hoping that the former House Speaker - rather than Romney - secures the Republican nomination.

With a picture of President Obama on the screen, the ad asks , "Why is this man smiling?" The answer: "Because his plan is working," the ad's narrator says. "Brutally attack Mitt Romney and hope Newt Gingrich is his opponent."

Romney is not alone by any means in attacking Gingrich. Michele Bachmann, who won the Iowa straw poll in August but has since faded, dubbed Gingrich "a poster child for crony capitalism" and "the ultimate consummate influence peddler." Ron Paul, who finished a close second to Bachmann at the Ames event, has unveiled slick web videos going after Gingrich. Jon Huntsman, who is not competing here in Iowa, called Gingrich a product of Washington "who participated in the excesses of our broken and polarized political system."

Even Democrats, who to date have focused their attacks on Romney, turned their sights toward Gingrich after seeing him skyrocket up the polls.

"For the longest time, Gingrich was not really a factor in this race, he was left for dead at the checkout counter at Tiffany's," quipped Obama strategist David Axelrod to the New York Times. "Now he is resurgent and he could be the nominee."

The flurry of attacks should come as no surprise to Gingrich: It's what happens when you're on top. Every poll released this week seemed to bring better and better news for Gingrich. An ABC News/Washington Post poll showed Gingrich in the lead with 33 percent support in Iowa, followed by Romney and Paul tied at 18 percent. In two other key early states - South Carolina and Florida - Gingrich also holds impressive leads of 23 percent, according to the most recent CNN-Time magazine polls. In addition, according to a Quinnipiac University poll of Florida, Ohio and Pennsylvania, Gingrich "cuts sharply into President Barack Obama's general election lead should he win the GOP nomination."

It's all enough to make some strategists wonder what took the rest of the Republican field so long to step up their attacks.

"My suspicion is they're all looking at themselves saying, 'Why didn't we start this weeks ago?'" veteran GOP strategist Karl Rove told Stephanopoulos on "Good Morning America."

It's all leading up to a fascinating - and potentially explosive - debate come Saturday night: There's the newfound clarity of the race, with the upstart Gingrich at the top, followed by Romney, with much more money and much stronger organization. There's the increasing intensity, as attacks come fast and furious from all sides. There's the unpredictability of the race, from Rick Perry to Herman Cain, as various candidates have surged to the front only to fall back into the pack. And don't forget the looming caucuses: Iowans vote on Jan. 3.

Thus far, the debates have played a key role in the race, from Gingrich's surge to Perry's plunge.

"Due to the debates and the campaign events that the candidates hold here in our state, it gives us the chance to know them better and know their campaigns better," said Enrique Peña-Velasco, a Des Moines businessman. "For us it's really helpful."

"Iowa is the hub of the political process in the United States, and it is always the place where the whole process begins to determine the fate of the national campaign," he added.

So how will Gingrich cope with the bullseye emblazoned on him these days? Perry, for instance, was so beaten down by his opponents' attacks that he joked at a September debate in Tampa that he felt like "a pinata." But Gingrich is trying not to take the bait.

"I'm going to stay positive, I'm going to talk about how we solve the country's problems," he said this week. "And I have one opponent: Barack Obama."

For their part, some Drake students are hoping the ABC debate brings forth some new ideas from the candidates on how to jumpstart the country's struggling economy.

"For me the most important topics are the economy - the economy and unemployment," said Joe Frake, a senior at Drake who is preparing to start his job search this winter.

Despite the fact that there is little time left before the caucuses, Iowa voters still appear open to changing their minds. According to the ABC poll, over half of the voters said they could still switch candidates.

"The last word belongs to the Republicans who go to the caucuses on January 3," said Drake Prof. Eduardo Garcia.

With the weather getting colder - Des Moines on Friday was blanketed in snow - and the GOP race heating up, Saturday's debate provides the candidates with one of their last opportunities to earn the support of voters.

Matthew Jaffe is covering the 2012 campaign for ABC News and Univision.