The politics of terrorism have returned with a vengeance for the midterm elections.

National security dominated the first election cycles after the attacks of Sept. 11, 2001, with Democrats fearful of being labeled unpatriotic if they criticized then-President George W. Bush.

The Republican advantage eroded years later as public opinion soured against the Iraq War. By the time President Obama sought reelection in 2012, he was able to tout the killing of Osama bin Laden to portray Democrats as the party of strength in foreign policy.

But now, with the 13th anniversary of 9/11 just days away, Obama and the Democrats are back on the defensive.

Obama’s response to the advances made by the radicals of the Islamic State in Iraq and Syria (ISIS) has provoked a chorus of criticism, including from vulnerable Democrats up for reelection this year.

And it’s not just the broad threat posed by ISIS that has changed the political landscape — Obama has given GOP critics an opening by fumbling several public statements.

One gaffe came during a recent press conference when he admitted that, when it comes to countering ISIS, “we don’t have a strategy yet.”

Former spokesman Robert Gibbs called it a “wince-able” moment.

Senate Democrats who are running for reelection in a tough political environment are sounding the alarm bell.

Sen. Al FrankenAl FrankenOvernight Cybersecurity: Senate sends Russia sanctions bill to Trump | Senators unveil email privacy bill | Russia tried to spy on Macron with Facebook OPINION | Democrats: Time to wish Hillary Clinton good luck and goodbye Franken: ‘Constitutional crisis’ if Trump uses recess appointment to replace Sessions with someone who’ll fire Mueller MORE (D-Minn.) fired off a letter to Attorney General Eric HolderEric H. HolderThe Memo: Justice Department veterans reeling over Sessions drama Manafort heads for Senate showdown after subpoena Holder: Voting commission's Kobach is a 'fact-challenged zealot' MORE demanding to know what the Justice Department is doing to intercept American jihadists returning from Syria.

“I was troubled by the president’s recent suggestion that the administration has not yet developed a comprehensive strategy to address the growing threat of ISIL’s activities in Syria,” he wrote, using an alternative acronym for ISIS.

Separately, Senate Republican Leader Mitch McConnellMitch McConnellLawmakers look forward after ObamaCare repeal failure McConnell: 'Time to move on' after healthcare defeat Senate ObamaCare repeal bill falls in shocking vote MORE (Ky.) pounced on Obama’s remarks during a trip to Estonia where he characterized ISIS as a “manageable” threat.

“This is not in my view a manageable situation. They want to kill us,” he warned.

It was a rare instance when some Democrats sided with McConnell over the president.

“Do not believe ISIL is ‘manageable,’ agree these terrorists must be chased to the ‘gates of hell,’ ” tweeted Sen. Jeanne Shaheen Jeanne ShaheenOvernight Cybersecurity: Senate sends Russia sanctions bill to Trump | Senators unveil email privacy bill | Russia tried to spy on Macron with Facebook Lawmakers push to toughen foreign lobbying rules Families make emotional plea for diabetes research funding MORE (D-N.H.), who is facing a tough reelection race.

Following the criticism, Obama on Friday tried to walk back his comments, saying ISIS must be destroyed and cannot be contained.

He will expand on that idea when he delivers a televised address to the nation on Wednesday. Previewing his message in an interview with “Meet the Press” Sunday, Obama said that he wanted the American people to understand ISIS is “a serious threat” but that “we have the capacity to deal with it.”

Democrats who could replace Obama in the Oval Office, including Vice President Biden and Hillary ClintonHillary Rodham ClintonSessions says he doesn't regret recusing himself from Russia probe Judiciary Committee Republicans want a second special counsel: report Fusion GPS: White House trying to smear us on Russia MORE, are also using more muscular foreign policy rhetoric. Biden has vowed to follow ISIS “to the gates of hell,” while Clinton has blamed the growth of ISIS on “the failure to help build a credible fighting force” against strongman Bashar Assad in Syria.

Republicans who are mulling their own quest for the White House in 2016 are attacking Obama’s foreign policy with gusto.

Texas Gov. Rick Perry (R) blasted the president for “dithering and debating” and “always playing catch-up” on international crises that threaten U.S. interests.

Sen. Ted CruzTed CruzSenate heading for late night ahead of ObamaCare repeal showdown Two GOP senators back ObamaCare repeal after Ryan call Senate releases 'skinny' ObamaCare repeal bill MORE (R-Texas) declared “we ought to bomb [ISIS] back to the Stone Age.”

Sen. Rand PaulRand PaulOvernight Defense: Military won't lift transgender ban until Trump sends directions | House passes national security spending | Russian sanctions bill heads to Trump Overnight Cybersecurity: Senate sends Russia sanctions bill to Trump | Senators unveil email privacy bill | Russia tried to spy on Macron with Facebook Senate sends Russia sanctions bill to Trump's desk MORE (R-Ky.), who in the past warned against foreign entanglements and called for ending foreign aid, declared in Time magazine, “I am not an isolationist,” and faulted Obama for letting a “jihadist wonderland” blossom in Libya and Syria.

Some Democrats are frustrated by what they see as a lack of clear leadership from the president.

“All of these members back in their home states have been getting asked about all of these foreign policy issues for the last couple weeks. Very few if any have gotten any guidance from the White House or indication about what the president is thinking,” said a Democratic strategist who has spoken with several lawmakers.

The consequence, the strategist added, is that some endangered Democrats are beginning “to flail about a little.”

There is a growing belief among policy experts that ISIS poses a greater national security threat than al Qaeda did before 9/11. The radical group is estimated to control billions of dollars in assets, and has trained American and European citizens who could return home to stage an attack.

“They have much more resources than al Qaeda did on 9/11. The whole 9/11 operation cost less than half a million dollars. [ISIS] has at least two billion dollars. My understanding is they’re selling oil on the black market for a million dollars a day,” said Rep. Pete King (R-N.Y.), the former chairman of the House Homeland Security Committee who might run for president in 2016.

“ISIS is right now more dangerous than al Qaeda was on 9/11,” he added.

Lee Hamilton, the former Democratic congressman from Indiana and vice chairman of the 9/11 Commission, defended Obama for taking a careful approach. He argued that Obama is smart to feel out allies such as the United Kingdom before rushing in.

“[Obama] wants some help and that makes sense to me,” he said. “You have a lot of strands here. What are we willing to do by ourselves? How serious is this threat? What are our objectives?”

But Hamilton said the president could do more to lead an international public relations effort to discredit militant Islamic movements.

“One of the things totally missing from the strategy, from my point of view, is a political strategy. If you’re going to destroy ISIS, what you’re really talking about is destroying an ideology. I’ve not seen anything as to how we’re going to do that,” he said.

The mounting political tensions over foreign policy could complicate any effort by Obama to win congressional approval for airstrikes inside Syria before the election.

Some vulnerable Democrats don’t want to vote on the issue for fear of depressing the liberal base right before an election in which turnout will be critical.

A Democratic leadership aide said Friday that a Senate vote on a new use-of-force resolution this fall is unlikely, but that could change depending on the mood of the caucus.

House Majority Leader Kevin McCarthy (R-Calif.) says House lawmakers will receive briefings on the Islamic militant group this week, but has not indicated whether a vote will occur.

One thing people affiliated with both parties can agree on — especially in the wake of the videotaped beheadings of two American journalists — is that terrorism is back, in a big way, as a political issue.

Former Sen. Byron Dorgan (D-N.D.) said the gruesome deaths had changed “the ranking of issues in this country.”

“I assume, if you did a poll this morning, that dealing with ISIS would be somewhere near the top,” he added.

“Had you done it six months ago, it probably would not have been on the poll’s list of questions.”