The latest Des Moines Register poll shows Texas Senator Ted Cruz surging to a 10 point lead over his nearest rival, Donald Trump, among caucus goers in Iowa.

Cruz’s October surge is the largest jump measured over 5 Presidential campaigns. Cruz currently has the highest favorability rating of any Republican candidate for President.

Cruz has 31 percent support, followed by Donald Trump with 21 percent. Since October, Cruz has gained 21 points while Trump has gained just 2 percent. Neurosurgeon Ben Carson is in 3rd place with 13 percent, down 15 points since October. Florida Sen. Marco Rubio is 4th with 10 percent support, essentially unchanged since the last poll.

Former Florida Gov. Jeb Bush is 5th with just 6 percent support. His Super PAC, Right to Rise, has been the biggest buyer of TV ads in the state, spending millions of dollars to support Bush’s campaign. In spite of the massive spending, Bush gained just 1 point of support since October. Worse, 41 percent of likely caucus goers say they would never support Bush.

“Based on this data, it’s hard to keep Bush in the picture,” said Ann Selzer, who conducted the poll for the Des Moines Register. It is important to note that Selzer is widely considered the guru of polling in Iowa. Her polling for Iowa races, both in the caucuses and in off-year elections, has proven to be the most accurate for what can be a difficult landscape to measure.

Based on Selzer’s track record, this poll likely provides the most accurate snapshot of the political terrain in Iowa today.

Cruz’s dramatic surge in Iowa may surprise most political reporters, whose time is consumed with following Donald Trump. It will likely also be a shock to most members of the Republican establishment, who, when they’re not wringing their hands over Trump, are trying to decide between Bush or Rubio as the moderate standard-bearer.

For those observers watching the latest developments on the ground, however, the Cruz surge is the natural culmination of a campaign focused on substantive policies and a serious ground game.

Cruz surprised many pundits early in the campaign when 4 super pacs supporting his candidacy announced they had raised $31 million in the 2nd Quarter, second only to Jeb Bush. His individual campaign itself has raised close to $30 million, just behind Ben Carson’s total and almost double Marco Rubio’s. Cruz’s fundraising is just behind Bush, when both the campaign and super pac are totaled together.

It is unusual for a conservative candidate running strongly against the party establishment to be so successful in fundraising. Cruz has even raised three times more in Texas than Bush, which is surprising given the Bush family’s strong ties to the Lone Star State.

The Cruz fundraising haul, though, speaks only to the potential of his campaign. Many candidates have experienced impressive bursts of fundraising, only to fade as the campaign wears on. In the last few weeks, however, Cruz has taken several steps that are starting to pay real political dividends.

“The coalescing has begun” for Iowa conservatives, Selzer said about Cruz’s rising support in Iowa.

This week, Cruz picked up the endorsement of Bob Vander Plaats, a leading figure among evangelicals in Iowa. Evangelical voters make up a significant share of the Iowa Republican caucus vote. The endorsement comes not long after Cruz earned the backing of Iowa GOP Rep. Steve King, a champion against President Obama’s amnesty executive order and a beloved figure among Iowa’s grass roots conservatives.

Cruz also won the backing of Steve Dease, a popular conservative talk radio host in the Hawkeye State. Winning the backing of Vander Plaats, King and Dease has been called the “trifecta” of Iowa Republican politics.

Also this week, Cruz picked up the endorsement of conservative pioneer Richard Viguerie. The conservative icon Viguerie is one of the architects of the modern conservative movement whose endorsement could unite national conservative figures behind Cruz. “Cruz is the only candidate who can unite the GOP. That is so important, because this will be a base election,” Viguerie told Breitbart News.

There were two other campaign developments this week, however, that perhaps go even further to explain the strong support coalescing behind Cruz. On Thursday, Cruz gave a speech focused on foreign policy at the Heritage Foundation. Echoing Ronald Reagan and Jeanne Kirkpatrick, Cruz outlined a robust strategy to combat radical terrorism without miring the US in overseas conflicts.

Eli Lake, a highly respected foreign affairs reporter for Bloomberg, tweeted out “Don’t agree w/ everything @tedcruz is saying, but this is a serious foreign policy speech that shows a mastery of the issues”

Cruz also last week convened a hearing of the Senate Subcommittee he chairs to examine the science behind many of the claims of climate change activists. The hearing drew loud protests from Democrats, and didn’t attract a lot of media attention. The hearing was important, however, because it occurred against the backdrop of the world climate talks in Paris. The hearing showcased Cruz’s focus on articulating conservative policies, even when the news cycle isn’t watching.

One final note about this week is worth considering. While most Republican candidates were following the media and condemning Donald Trump’s proposal to temporarily block Muslim immigration, Cruz focused instead on his own plans. An under appreciated aspect of conservative frustration with the Republican establishment is that it meekly follows the media, rather than stand up to it.

Cruz did his best in the debates when he turned absurd questions back on the reporters who seemed more interested in debating the candidates themselves. Cruz’s attack on the media during the CNBC debate, in fact, generated the most positive response ever measured in a focus group convened by pollster Frank Luntz.

Cruz continued his criticism of the media this week, even taking a swipe at the Wall Street Journal editorial page, which has long been the paper of record for the Republican establishment. “For the next three months, the Journal should change their header to the ‘Marco Rubio for President Newspaper,” Cruz said on MSNBC’s Morning Joe program.

For the past month, the Republican establishment has grown apoplectic over fears that Donald Trump would capture the party’s nomination. There could be an even more serious threat to the establishment building in Iowa, however. The establishment may win its battle against Trump, but lose its war against Cruz.