As the nation's midsection has grown more conservative and Republican, Democrats have sometimes had to rest their hopes on well-positioned GOP contenders imploding with their own politically off-key statements.
It worked like a charm for Democrats in 2012 when Republican candidates in Indiana and Missouri blew winnable Senate races after provocative comments on rape and abortion.
But with less than four months until the 2014 election, Democrats are still waiting for new bombshells and growing more anxious about the lack of incendiary material as they try to hold enough Senate seats to keep control of the chamber. Party researchers are diligently scrubbing every transcript and public comment for a hint of fringe language that might spook moderate or independent voters.
"When you get a gift like that, you dream about another gift," said Carter Wrenn, a North Carolina Republican strategist, referring to the 2012 Missouri and Indiana Senate results.
The best Democrats have come up with so far is Iowa Republican Senate candidate Joni Ernst's avowed belief in a possible threat to American property rights posed by an obscure global development concept known as Agenda 21. Some conservatives see the concept as the harbinger of a United Nations takeover.
"Agenda 21 is a horrible idea," Ernst told a rural county GOP audience in November.
The non-binding resolution, signed by Republican President George H.W. Bush in 1992, urges nations to conserve open land and steer development toward more populous areas.
Ernst said last year: "The implications we could have here is moving people off their agricultural land and consolidating them into city centers, and then telling them 'you don't have property rights anymore.' These are all things that the UN is behind, and it's bad for the United States and bad for families here in the state of Iowa."
Susan Geddes, a conservative Iowa Republican strategist, said Ernst's characterization "is a problem for our party." Conspiracy theories aren't good campaign issues, she said.
"I don't know why she'd say that," said Geddes, a senior Iowa adviser to Mike Huckabee's 2008 presidential campaign.
The Iowa Democratic Party has been citing the remark, and Ernst's calls for impeaching President Barack Obama, in press releases in hopes of building a case that Ernst's views are outside the mainstream. It's not clear whether they are having an impact in her race against Democrat Bruce Braley, which appears to be close.
Ernst campaign spokeswoman Gretchen Hamel called the reference to the remarks "a desperate attempt to change the subject away from Braley's liberal record."
The bombshell problem has increased as Republicans have gotten stronger in regions such as the Midwest, which was once more evenly divided between the parties. The more conservative GOP candidates winning primaries now are more inclined to play to the party's rightmost fringe, saying things that can trouble voters in a general election. Controversial remarks often relate to women's issues, religion, race or government plots.
Former Mississippi Sen. Trent Lott's praise of former segregationist Republican Strom Thurmond in 2002 cost him his Senate GOP leadership status. In 2012, Missouri GOP candidate Todd Akin's Senate campaign crumbled after he declared the female anatomy capable of preventing pregnancy in the case of "a legitimate rape." Likewise Indiana Senate candidate Richard Mourdock's bid sank after he said pregnancies that result from "that horrible situation of rape, that is something God intended to happen."
The more cautious rhetoric in 2014 has come as a relief to national GOP leaders who want to close the Democrats' edge with women, younger and minority voters. Last year, the party had a series of candidate training sessions on speaking carefully.
The GOP needs to gain six seats to win Senate control. In addition to Iowa, Republicans are locked in tight races in Arkansas, Colorado, Michigan, Louisiana, Kentucky and North Carolina.
"There has been a concerted effort early on to introduce these positions that Republicans hold as extreme," said Justin Barasky, national press secretary for the Democratic Senatorial Campaign Committee. Meanwhile, Republican candidates are portraying their opponents as the allies of Obama's health insurance program.
Democrats are trying to highlight comments by North Carolina Republican Thom Tillis in 2012 about demographic changes in the state as part of what they call his "history of divisive and offensive comments." While the ethnic population is growing, "the traditional population in North Carolina and the United States is more or less stable," Tillis said. North Carolina Democratic consultant Gary Pearce acknowledged the remark is no game-changer.
For Democrats, the search continues for words that suggest fringe views.
"If it sticks they're delighted and if it doesn't they move on to the next thing," North Carolina Republican Wrenn said.