This new Q-poll gives Republicans some good news — but also a huge reason for concern. Joni Ernst led in last week’s Quinnipiac survey by two (48/46), and this result is still a change within the margin of error. Still, a four-point lead six days out from an election, where the one-time underdog just barely misses a majority, is a significant piece of news:

Iowa Republican State Sen. Joni Ernst is inching ahead among likely voters in the U.S. Senate race and now has 49 percent to 45 percent for U.S. Rep. Bruce Braley, the Democrat, according to a Quinnipiac University poll released today. Five percent remain undecided.

This compares to results of an October 23 survey by the independent Quinnipiac (KWIN- uh-pe-ack) University, showing Sen. Ernst at 48 percent and Rep. Braley at 46 percent.

Today’s results show independent voters backing Ernst 50 – 41 percent. Republicans back Ernst 90 – 4 percent. Democrats go to Braley 94 – 4 percent.

But here’s the part that will give Republicans night sweats all week long:

Braley leads 57 – 36 percent among those who already have voted.

A twenty-one-point lead among early voters for Braley? That’s a whopping advantage, especially when looking at the early-voting statistics published by the state of Iowa. As of yesterday, the state had received 348,968 absentee ballots, about 72.4% of all those requested by Iowa voters. Republicans usually lag badly in Iowa’s early voting; this year they’re competitive, but still behind by 5,145 ballots (39.6% to 41.1% for Democrats). The number of requests so far (481,970) come to nearly half of the total number of ballots cast in the 2010 gubernatorial election (1,047,714).

If Braley has anywhere near this kind of lead in early balloting, it would mean that either the Democrat is carrying practically all of the independents, which account for 19.1% of all returned ballots, or Republican crossover for Braley is significant. In the breakdowns for the candidates in Quinnipiac’s data, though, we don’t see anything of the sort. Only 4% in either party cross over to the other candidate, and Ernst has a nine-point lead among independents. Furthermore, while Braley’s favorables are much higher among those who have already voted, overall Braley’s underwater 40/43 while Ernst gets a 45/43.

Either one has to conclude that the Q-poll’s sample of early voters is so small as to generate wide disparities, or the overall poll result is way off. Other polls show roughly the same trend in the race’s topline, so the sample of likely voters seems suspect, although it accounts for 33% of the overall sample, with a 5.68% margin of error. Something is very screwy with the early-voting survey, it seems.

Otherwise, as McClatchy notes, the early-vote trend looks pretty good for Republicans this year, at least compared to the last two cycles:

Aggressive outreach is drawing in new voters, as Republicans play catch-up to the Democrats’ early-vote turnout machinery.

In Georgia and North Carolina, for example, about 22 percent of this year’s early voters have no records of voting in the 2010 midterm elections, according to Michael McDonald, a University of Florida political science associate professor who compiles early voting data for the United States Elections Project. …

In Iowa, where Republican Joni Ernst and Democratic Rep. Bruce Braley are vying for the open Senate seat created by the impending retirement of Democrat Tom Harkin, Republicans last Wednesday trumpeted figures released by Iowa’s election offices that showed them outpacing Democrats in early votes for the first time in two election cycles.

The Republican lead was 305 votes, small but significant, considering that Democrats led Republicans at this point in 2012 by 56,908 ballots and by 16,426 ballots in 2010. After being outpaced by Democrats in early votes, Republicans nationally have stepped up their efforts with the help of outside groups such as the conservative Americans for Prosperity, which has poured in $125 million to improve conservative-voter turnout efforts.

“We’ve completely revamped our ground game, putting an emphasis on turning out low-propensity voters before Election Day, and it’s working,” Republican National Committee Chairman Reince Priebus said of the Iowa numbers last week. “The Democrats can spin all they want, but they’re in trouble in a blue state.”

But the lead flipped last Thursday and Democrats moved ahead by 463 ballots, McDonald said. Of Iowa’s 306,369 returned ballots, about 41 percent were from Democrats, 40 percent from Republicans and 19 percent from unaffiliated voters, according to the United States Elections Project.

There’s more work to be done for 2016, but the GOP appears to be on the correct path, and look at least competitive in this cycle.