By Niall Stanage, The Hill–

The FBI rocked the presidential race Friday by announcing that more emails pertaining to its investigation of Hillary Clinton‘s server had been uncovered and that the bureau was taking “appropriate investigative steps.”

The statement, from FBI Director James Comey, came with just 11 days to go before Election Day and after more than 12 million early votes had already been cast .

Clinton is the heavy favorite to win the presidential race based on national and battleground state polls, but the FBI’s announcement had the feel of an “October surprise” that could upset the contest.

The statement introduced a new and potent element of volatility into the closing stages of the campaign.

The negative news for Clinton could also have serious ramifications in down-ballot races across the country.

It could be a particularly big factor in which party controls the Senate, a battle where each party’s fortunes have been tied closely to the White House contest.

Democrats have been hoping that resistance to Republican presidential nominee Donald Trumpwould be the catalyst for a wave election that would net the minimum of four seats they need to take back the Senate majority.

Republicans are favored to keep their majority in the House, but election handicappers in recent days have been shifting more races toward Democrats. The dramatic FBI news would seem to bolster the GOP’s chances in both the Senate and the House.

Congressional Republicans seized on the report.

Speaker Paul Ryan (R-Wis.), who has distanced himself from Trump and the presidential race, said in a statement that Clinton had “nobody but herself to blame” and called for her classified briefings to be suspended.

Republican National Committee Chairman Reince Priebus said that the “stunning development raises serious questions about what records may not have been turned over and why.” Rep. Pete King (R-N.Y.) told MSNBC’s Kate Snow that the situation was “totally unprecedented.”

Trump used the news to buttress his case that Clinton was culpable of “corruption … on a scale we have never seen before.” When the GOP nominee told a crowd at a rally in Manchester, N.H., about the breaking news, he was almost drowned out by raucous cheers.

Aides to Trump were jubilant. The GOP nominee’s campaign manager, Kellyanne Conway, tweeted that “a great day for our campaign just got better.”

By contrast, Democrats sought to stave off questions on the issue.

The Democratic nominee offered no response in her first public appearance in the wake of the news, at a rally in Iowa. A short time later her campaign chairman, John Podesta, issued a statement that took aim at Trump and the GOP for “baselessly second-guessing the FBI.” Podesta also asserted that it was “extraordinary that we would see something like this just 11 days out from a presidential election.”

Clinton’s running mate, Sen. Tim Kaine (D-Va.), told a reporter who asked about the new probe that he would have to “read a little more” before he could offer a comment. Donna Brazile, the interim chairwoman of the Democratic National Committee, tweeted simply “Good grief.”

It was not clear exactly what Brazile meant by that tweet, though some liberal voices on social media have implied that Comey, a Republican, could be seeking to influence the outcome of the elections.

It will be hard to make that accusation stick, however, given Comey’s straight-arrow reputation and his earlier decision not to recommend charges against Clinton — a judgment that drew considerable criticism from Republicans.

Clinton supporters have been buoyed by her lead in the polls and the fact that there were no big events expected before Nov. 8 that could knock her off course.

Now, the former secretary of State must deal with a potentially toxic story in the homestretch.

The announcement came without warning. The email issue had been a millstone weighing on Clinton’s campaign, but it appeared to be behind her after Comey announced this summer that she would not be indicted. Now, the burden is back on her shoulders.

In July, after a yearlong investigation, the director criticized Clinton and her aides for being “extremely careless in their handling of very sensitive, highly classified information,” particularly the former secretary’s use of a private email system for government business.

The three-paragraph statement from Comey on Friday, in the form of a letter to the chairmen of congressional committees, did not offer many details. It said that “in connection with an unrelated case, the FBI has learned of the existence of emails that appear to be pertinent to the investigation.” It added that investigators would “review these emails to determine whether they contain classified information.”

The New York Times and, later, The Associated Press reported that the unrelated investigation that brought the emails to light is focused on former Rep. Anthony Weiner (D-N.Y.), who has been enmeshed in several scandals involving sexting. Weiner is married to, but separated from, Huma Abedin, one of Clinton’s closest aides.

One Republican senator, John Cornyn of Texas, expressed curiosity on Twitter about why the FBI would take this action now, so close to the election. In later tweets, the senator mused that they bureau would only do so if it were looking at serious wrongdoing. There is, however, no independent evidence of that.

The story will clearly dominate the news through the weekend and Clinton’s first comments, whenever they come, will create a media frenzy.

The Democratic nominee’s supporters will hope that concerns about her trustworthiness are already baked in to the electorate’s view of her.

But it is just as plausible that the dramatic twist could upend this year’s turbulent race one more time.