Republican state Sen. Joni Ernst faces Democratic U.S. Rep. Bruce Braley for Iowa's open Senate seat.(Photo: AP)

DES MOINES, Iowa — Joni Ernst has charged to a 7-point lead over Democrat Bruce Braley in a new Iowa Poll, which buoys the GOP's hope that an Iowa victory will be the tipping point to a Republican takeover of the U.S. Senate.

Ernst, a state senator and military leader, enjoys 51 percent support among likely voters. That's a majority, and it's her biggest lead in the three Iowa Polls conducted this fall. Braley, a congressman and trial lawyer, gets 44 percent, according to The Des Moines Register's final Iowa Poll before Tuesday's election.

"This race looks like it's decided," said J. Ann Selzer, who conducted the poll for The Register. "That said, there are enormous resources being applied to change all that."

The news will thrill Republican activists nationwide, who are counting on Iowa as an anchor for regaining the majority in the U.S. Senate. On Saturday, a progressive group organized a conference call with Majority Leader Harry Reid to urge Iowa Democrats "to double down and save the Senate."

"If we win Iowa, we're going to do just fine," he said. "Iowa is critical, there's no other way to say it."

It's hard to see much in these poll results that Braley could capitalize on to build a groundswell, Selzer said. "None of this looks good for him," she said.

Braley has lost vote share since an early October Iowa Poll (he dropped from 46 percent to 44 percent) while Ernst has increased her share (from 47 percent to 51 percent now).

Another sign of trouble: Braley is losing by 3 points in his home congressional district in left-leaning northeast Iowa. In the early October poll, he was up by 1 point there.

Here's what has shaped Ernst's lead, according to the poll results:

• Although a small plurality of likely voters think Braley has more depth on the issues, they like Ernst better on several character descriptions. They think she better reflects Iowa values, she cares more about people like them, and she's more of a regular, down-to-earth person.

• Voters find Ernst, who has led Iowa troops in war, to be a reassuring presence on security issues, the poll shows. In the wake of news developments on the Ebola outbreak in West Africa, increasing aggressiveness of Russia and the rise of the Islamic State in the Middle East, more likely voters see Ernst as better equipped than Braley to show leadership and judgment, by at least 9 points on each issue.

• Independent voters are going Ernst's way, 51 percent to 39 percent.

• The negativity in the race has hurt Braley more than Ernst. Forty-four percent say he has been more negative in campaign ads, compared with 32 percent for Ernst.

• Among several potential mistakes the two candidates have made, the one that stands out is Braley's seemingly condescending remark about Republican Sen. Chuck Grassley. In March, GOP operatives released caught-on-tape remarks  Braley made at a private fundraiser in Texas that seemed to question the qualifications of "a farmer from Iowa without a law degree" to become the next chairman of the Senate Judiciary Committee.

That inflicted a lingering hurt, as did emergence of the news that Braley had missed the majority of his Veterans Affairs Committee hearings, the poll shows.

Negative TV advertising by GOP outside groups relentlessly pushed those two pieces of damage.

Selzer said Braley failed to clean up his mess on the Grassley mistake. "He seemed to think it just didn't matter," she said.

On the same day the video of his remark hit national news, Braley apologized to Grassley and "anyone I may have offended."

"That didn't do it," Selzer said. "He never explained it."

• Ernst has been hurt, but not as deeply, by her relationship with the Koch brothers, two billionaire tea party activists who have helped her campaign with advertising and money, and by her stance that private accounts for Social Security could be an option, the poll shows.

The Iowa Poll of 701 likely voters in the 2014 general election was conducted Oct. 28-31 by Selzer & Co. of Des Moines and has a margin of error of plus or minus 3.7 percentage points.

Four percent of likely voters remain undecided. Only 7 percent who have made a choice say they could still be persuaded to vote for another candidate.