From the moment Democratic presidential candidate Hillary Clinton entered the race in April, she widely was considered the party’s presumptive nominee. Now, for the first time since she began campaigning earlier this year, that position may be in jeopardy.

A Bloomberg Politics/Des Moines Register poll released Saturday indicated Vermont Sen. Bernie Sanders polling at 30 percent among Iowa Democrats, within single digits of Clinton's 37 percent.

The survey of 804 likely Democratic caucusgoers, conducted Aug. 23-26, represents a sharp decline in the former secretary of state’s popularity with voters from the Hawkeye State -- an earlier Bloomberg/DMR poll from May had Clinton polling at 57 percent compared to Sanders’ 16 percent.

"It looks like what people call the era of inevitability is over," J. Ann Selzer, an Iowa pollster whose organization conducted the survey, told Bloomberg. "She has lost a third of the support that she had in May, so any time you lose that much that quickly, it’s a wake-up call.”

HillaryClinton_AFLCIO Hillary Clinton responds to a question at the AFL-CIO Presidential Forum at Soldier Field in Chicago on Aug. 7, 2007. Photo: Reuters/John Gress

Vice President Joe Biden, who has yet to announce whether he will enter the race, came in third place with 14 percent of the vote, up from just 8 percent in May. Biden is expected to make a final decision and announcement by the end of September.

But the vice president’s increased likelihood of running in recent months is not the only explanation for Clinton’s drop. When removing Biden from the mix, Clinton remained within single digits of Sanders, polling at 43 percent compared to Sanders at 35 percent.

The margin of error for the poll is 4.9 percentage points. The other declared Democratic candidates, former Maryland Gov. Martin O’Malley, former Sen. Jim Webb, D-Va., and former Rhode Island Gov. Lincoln Chafee, continued to poll in the low single digits, Bloomberg said.

The results are Sen. Sanders best to date in Iowa. In previous Iowa polls, Clinton has led the Vermont senator by a minimum of 19 percentage points, and Real Clear Politics’ polling aggregator showed Clinton’s average lead in the state to sit at 22.8 percent more than Sanders.

And unlike his lead in New Hampshire polls, skeptics cannot claim there is a regional bias in Sanders' favor in Iowa.

But the Vermont lawmaker's lead in this poll does not necessarily mean Clinton is on a serious decline. A Suffolk University poll released earlier in the week indicated Clinton had 54 percent compared to Sanders at 20 percent -- a much healthier lead for the former secretary, Salon reported.

2015-05-27T175023Z_1825413105_GF10000109251_RTRMADP_3_USA-ELECTION-SANDERS Democratic presidential candidate Sen. Bernie Sanders, Ind-Vt., uses a bullhorn to speak to supporters gathered outside a campaign stop at New England College in Concord, New Hampshire, on May 27, 2015. Photo: Reuters

Nevertheless, the shakeup in the polls reminds some of eight years ago. "This feels like 2008 all over again,” said Selzer, according to the Des Moines Register.

And there are similarities. In the 2008 Democratic presidential primary race, Clinton led then-Sen. Barack Obama by 7 points in an early October poll in Iowa. By late November, he had surpassed her, bolstered by the youth vote and first-time caucusgoers.

In this cycle, young Democrats and first-time caucusgoers have leaned toward Sanders, who holds 43 percent of their vote compared to Clinton’s 31 percent. Sanders also leads Clinton by 23 percentage points with the under-45 crowd, the Des Moines Register said.

Sanders is also genuinely popular with his voters. A massive 96 percent of respondents who supported him said they chose him because they genuinely like his ideas and positions -- not that they are merely opposed to the former first lady.

“These numbers would suggest that she can be beaten,” said Steve McMahon, a Democratic strategist based in Virginia, according to the Des Moines Register. “But it’s still early,” he added, “and Hillary Clinton’s done this before. She knows what it takes to win.”

The people polled, for the most part, agree. According to the Bloomberg/DMR poll, almost two-thirds of respondents are “mostly confident” Clinton could win the general election if she is selected as the nominee, with 24 percent “mostly nervous” about her ability and 9 percent who were unsure.