Time is running out for Sen. Luther Strange (R-Ala.), who has just one month to save his Senate term and pull off a come-from-behind victory against former Alabama Supreme Court Chief Justice Roy Moore in the race for the Republican nomination to finish out the Senate term of Attorney General Jeff Sessions.

The two sides have been in a relative stalemate since the Aug. 15 GOP primary, when Moore's failure to secure a majority of the vote sent him to a Sept. 26 runoff with second-place finisher Strange. Now the race is about to heat back up, with the Senate Leadership Fund (SLF) beginning a $3 million ad campaign this week supporting Strange.

The incumbent needs the help from the super PAC, which is aligned with Senate Majority Leader Mitch McConnell (R-Ky.). While Moore rode to the runoff relatively unscathed, Strange only secured the second spot after an ugly intraparty fight that seems to have bruised his image. And while President Trump's endorsement gave Strange a boost in that first round, the president hasn't campaigned hard for Strange ahead of the runoff.

Recent major swings in polling on the race underscore the unpredictable nature of a special election runoff, with few voters expected to turn out.

Two polls from last week showed Moore holding a double-digit lead over Strange. But two more recent polls, including an internal SLF poll, found Moore's lead down to the low single digits.

So while Strange and his well-funded allies prepare to flood the zone with ads attacking Moore, it remains to be seen whether the concerted attack will dampen Moore's strong base of support.

"None of these polls are perfect, to say the least. But they all have one common thread: Moore is leading in all of them. That should be disturbing for Strange and his supporters," said Geoffrey Skelley, a political analyst at the University of Virginia.

"Strange's position is far from ideal. He can still win, but if he's going to win, he's going to look at a very narrow path."

Most primary runoffs have low turnout, especially in special elections. So the race appears to be shaping up into a battle between Moore and his enthusiastic supporters on one side and Strange's superior campaign infrastructure and resources on the other.

Moore earned his stripes in high-profile battles that endeared him to the religious right - first over his defense of a Ten Commandments statue he commissioned on state grounds and another for his refusal to follow the Supreme Court's landmark ruling legalizing gay marriage nationwide

Through it all, he's carved out strong support among ardent conservatives while alienating others.

A recent poll from Decision Desk and Opinion Savvy shows Moore has twice Strange's support among evangelicals and those who identify as very conservative. But that trend flips with non-evangelical voters, with Strange running far closer to Moore among voters closer to the center of the political spectrum.

"Moore has consistently had a solid core, entirely consistent group. ... His voters are more fervent and ardent and more likely to vote," said former Alabama state Rep. Steve Flowers (R).

"There's no route to victory for Luther unless he can peel people off of Moore, which will be difficult."

That's exactly what the SLF will attempt to do as it begins to kick off its advertising onslaught. The group led the charge during the first round of voting as it filled the airwaves with attacks against Rep. Mo Brooks (R-Ala.), who was battling with Strange for the second ticket to the runoff.

Now the group can train the full force of its operation on Moore, who was able to slip through the primary without a scratch.

"Roy Moore has gotten a free ride. My bet is that changes," one Senate GOP aide told The Hill.

Some of those ads are expected to center on Moore's wife's nonprofit. The group began hitting Moore for alleged impropriety at that charity in the last days before the primary vote. Since then, lawyers told AL.com that the foundation could be violating tax rules by boosting Moore's campaign.

"Those gunslingers in Washington, with all that money, they may know something about Moore that we don't," Flowers said.

But going negative has its disadvantages.

Many Alabama Republicans believe that Strange's sagging favorability score came in part because of voter frustration with negative attacks from his allies. And Strange is already vulnerable to concerns about his association with disgraced former Gov. Robert Bentley (R), who appointed him to the seat earlier this year.

That's why Brent Buchanan, a veteran GOP strategist in the state, told The Hill that Strange has to "boost his positives with voters to have a shot."

He also added that Strange needs to take the focus off of national issues - a big liability for someone being framed by his opponent as a tool of the Beltway establishment.

But Strange supporters say the race is largely going according to plan. Strange's campaign and the SLF buried Brooks in the first round, a feat they can now pull off again with Moore, thanks to their significant resource advantage.

"If you look at the number of primary voters available to each candidate, the dynamics, and then the resources and organization available, you see a picture of someone who can expand significantly," a Senate GOP aide said.

"There's not a lot of room for growth for a candidate like Roy Moore."

Strange also has a wildcard: Trump. While a source familiar with the conversations told The Hill that Trump and Vice President Pence spoke to Strange last week to reiterate their support and discuss potential campaign events, Trump has stayed quiet on the race for weeks.

Trump, who is openly feuding with McConnell, hasn't held a fundraiser or agreed to campaign on Strange's behalf. And The Washington Post reported last week that Trump's allies are advising Trump to keep his distance from Strange.

On top of that, former White House chief strategist Stephen Bannon is backing Moore, according to a Politico report.

Strange allies believe the president isn't insulating himself from the fallout of a potential loss by distancing himself from Strange.

"The administration has a lot of skin in this game - more so than they'd like to admit - about Luther getting along the finish line here. The message it sends to his colleagues if he doesn't is that the administration will count on you to be there every time but won't stick their neck out for you if you're in trouble," the Senate GOP aide said.

"The die is cast, and it would be a tremendous embarrassment to this administration if they were to reverse themselves."