海角大神

Democratic Senate incumbents have proven surprisingly resilient ahead of November鈥檚 midterms. But even if vulnerable Democrats manage to hang onto their seats in other states, Iowa may be the Achilles鈥� heel in the party鈥檚 quest to keep the chamber blue.听

In a race that was once a dead heat, Republican Joni Ernst has pulled ahead of Democrat Rep. Bruce Braley in recent polls. Saturday鈥檚 Ms. Ernst capturing 44 percent of the vote to Representative Braley鈥檚 38 percent. Another poll from two weeks ago gave Ernst聽聽a similar lead, with others showing the race to be a tie.

鈥淏raley as a candidate was expected to be strong: a sitting congressman running against a fairly unknown person,鈥� says Tim Hagle, a political science professor at the University of Iowa. 鈥淏ut Braley lost that edge through a number of mistakes.鈥澛�

As Braley has underperformed, other Democrats have outperformed expectations. Sen. Kay Hagan (D) of North Carolina has consistently fended off her Republican opponent Thom Tillis in the polls. The New York Times 鈥渟ome of the best news for Democrats in this battle for Senate control.鈥� And while Alaskan Sen. Mark Begich has slipped behind his Republican challenger in the latest polling, the race is tight 鈥� and Senator Begich鈥檚 numbers are especially strong, given that .

It could be the money keeping Democrats afloat. Incumbents tend to have more of it, and Democrats have in key states. Earlier this month, GOP strategist Karl Rove fretted that Senate Democrats鈥� advertising and fundraising edge could spoil Republicans' shot at winning the chamber.听

鈥淩epublican candidates and groups must step up if they are to substantially reduce that gap,鈥� Mr. Rove wrote in the Wall Street Journal.听

But even if some of the Democrats once thought to be vulnerable squeak back into office, a candidate like Ernst could help the GOP take the Senate.

Ernst鈥檚 rise in the polls was something of a surprise. Before the GOP primary, Braley was thought to be the heir apparent of retiring Democratic Sen. Tom Harkin. Top GOP candidates passed up the chance to run against Braley. But relatively unknown Ernst聽emerged from the primary a robust challenger with an Iowa-friendly profile: a mother who served in Iraq and was raised on a farm.

Meanwhile, gaffes have plagued Braley. In March, Braley was caught calling popular Republican Sen. Chuck Grassley 鈥溾�� His campaign has tried to bolster his agriculture credentials 鈥� but a press release promoting his farm acumen misspelled basic terms like 鈥渄etasseling鈥� and 鈥渂aling,鈥� and a picture of a farm posted to his Facebook page turned out to be.听

鈥淲hen you鈥檙e trying to shore up your farming cred, you can't make those mistakes,鈥� Mr. Hagle says. 鈥淭he combination of those things allowed the race to close up.鈥澛�

Ernst has transformed the race into a hand-wringer for Democrats. Her strengths have made it possible that the GOP鈥檚 map to a Senate majority could run through Iowa 鈥� a state that twice voted for Obama. Still, 12 percent of likely voters remain undecided in the most recent poll, and Election Day is more than a month away.

In the first debate of the race, Braley and Ernst sparred Sunday over the usual smorgasbord of issues: Obamacare, immigration, and abortion. Braley tried to cast Ernst as a tea party extremist, out of touch with Iowa.听

"This election is about a clear choice between moving Iowa forward or following a radical tea party agenda that's going to take us backwards," Braley during the debate.

Braley also criticized Ernst for getting support from the Koch brothers 鈥� industrialist billionaires whom Democrats have tried to vilify for their outsize spending on behalf of conservative candidates.

In one of the debate鈥檚 more rousing rejoinders, Ernst pushed back: 鈥淐ongressman Braley, you鈥檙e not running against these other people,鈥� she. 鈥淵ou鈥檙e running against me.鈥�