With just a week left until the Iowa caucuses, the “outsider” presidential candidates Donald Trump and Ted Cruz appear to be building momentum over “establishment” candidates.

The Real Clear Politics (RCP) average has the real estate mogul Trump and Texas Senator Cruz combining for 60.8 percent among likely caucus goers. Florida Senator Marco Rubio and former Florida Governor Jeb Bush, the top polling establishment choices, combine for only a 15.4 percent stake of likely caucus goers.

The RCP average, though, has shifted since the January 14 debate, with Trump opening up a 6.4 percent lead on Cruz in what was previously a deadlocked race.

The last few weeks have seen Trump raise new attacks on Cruz, to which Cruz has responded rather than balking at the real estate mogul’s jabs as he has done in the past. Cruz has taken swings at Trump for his “New York values” while Trump has continued posing questions regarding the Texas senator’s eligibility to be President as a “natural born citizen” despite his Canadian birth.

Both of the two new polls included in the average completed interviewing on January 21, two days after Trump gained the endorsement of Sarah Palin, the former Alaska governor and one-time vice presidential candidate. Palin’s support was viewed as a potential advantage to Trump among evangelical voters, a group which usually has made up a majority of Iowa’s Republican caucus-goers. The two most recent polls found Trump and Cruz near even among white evangelicals.

Iowa Governor Terry Branstad’s bombshell anti-endorsement of  Cruz has also contributed to Trump’s recent surge. Branstad said last week that Cruz’s opposition to a renewable fuels standard “could be very damaging” for ethanol and thus the state of Iowa. Trump has backed the fuels

standard. When asked if he’d like the Texas Senator to lose, Governor Branstad said, “Yes.”

The question of the Iowa race for both parties has been whether the upstart candidates can bring new voters to the state’s caucus sites, which will largely determine the outcome. Both Trump and Vermont Senator Bernie Sanders, who is caucusing with the Democrats, have  appealed to potential first-time caucus-goers.

A Fox News poll in Iowa released Sunday shows those who have participated in the caucuses before are closely split between Trump and Cruz, while those who are new to the process are boosting Trump’s numbers. Trump’s bombastic rhetoric touches a nerve with right-leaning Independents, who have to register as members of the Republican Party to caucus for the real estate mogul.

As of now, the number of registered Republicans in Iowa has not increased significantly since the start of the election cycle. In addition, caucus-goers are generally more ideologically extreme than voters who participate in primaries, which also benefits Senator Cruz.

Iowa has not had a recent history of picking GOP nominees; its two previous caucus winners are former Pennsylvania Senator Rick Santorum and former Arkansas Governor Mike Huckabee. By contrast, the previous two New Hampshire winners, former Massachusetts Governor Mitt Romney and Arizona Senator John McCain, both went on to be the GOP nominee in their respective years.