WASHINGTON — All of Washington is girding for a critical health care vote next week, but national Republicans have diverted some attention south — sending money and even manpower to the Sept. 26 Senate primary runoff in Alabama that is dividing the party between the conservatives and the even-more-conservatives.

President Trump is scheduled to campaign for Republican Sen. Luther Strange in Huntsville on Friday, and Vice President Pence is slated to attend a Strange rally in Birmingham on Monday.

“I am supporting 'Big' Luther Strange because he was so loyal & helpful to me!’’ Trump tweeted Wednesday.

Sarah Palin, the former Republican vice-presidential nominee, is expected to stump Thursday in Montgomery for challenger Roy Moore, a controversial former Alabama chief justice who is running a campaign directly targeting "the establishment" in Washington.

“It’s a huge deal that conservatives across America are uniting behind Roy Moore to win this Senate seat because conservatives, frankly, are sick and tired of politicians running as conservatives and going to Washington and acting as moderates and liberals," said Bill Armistead, chairman of Moore’s campaign.

The special election, which polls suggest is a very close race, has garnered more national attention leading up to next week's runoff. Strange and Moore are competing for the Senate seat of now-Attorney General Jeff Sessions. Strange was appointed to replace Sessions in February.

Moore finished ahead of Strange in the Aug. 15 primary and has led in several polls. Next week’s winner will face Democrat Doug Jones, a former U.S. attorney, in the general election Dec. 12. While either Republican would be a strong favorite in the general election, Democrats think they could have a better chance against the ultra-conservative Moore.

Trump is throwing his muscle behind Strange, particularly with Friday's trip to Alabama.

“It puts an exclamation point on the fact that he supports Strange,’’ said Jennifer Duffy, senior editor at the nonpartisan Cook Political Report. “It does not hurt, not at all.’’

Luther Strange, the new Republican senator from Alabama, moves on March 29, 2017, into the office suites of former Alabama senator Jeff Sessions. Sessions, also a Republican, is now serving as attorney general.

The Senate Leadership Fund, a political action committee tied to Senate Majority Leader Mitch McConnell, R-Ky., plans to spend $1.5 million on radio and television ads this week to bolster support for Strange.

Strange supporters said Trump’s decision to campaign for the senator in Alabama will provide a critical boost. 

“I think the one endorsement … that matters more than anything in this race is President Trump because he’s just so overwhelmingly popular in Alabama,” said Chris Pack, the fund's spokesman. “We think that will make a difference.”

Both Strange and Moore have touted their support for Trump’s agenda.

Armistead called it “puzzling’’ that Trump and Pence would stump for Strange.

“We don’t understand why they’re doing what they’re doing because they would have no greater supporter in the Senate than Judge Roy Moore for Trump’s agenda,’’ he said. “We’re solidly on board with all the things that he’s trying to accomplish.’’

While Trump is popular in Alabama, Armistead said,  “it is very difficult to transfer one’s popularity to someone else.’’

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The Senate Leadership Fund got in the race early and has only intensified its efforts in the days leading up to next Tuesday’s runoff.

“Their job is to protect their incumbent. Strange is an incumbent,’’ said Duffy.

The support comes despite controversy over Strange’s appointment to the seat. Former Alabama governor Robert Bentley appointed Strange, then the state’s attorney general, to fill Sessions' seat.

Strange accepted the appointment in February even as his office was investigating the governor. Two months later, Bentley pleaded guilty to two misdemeanor campaign finance violations and resigned from office.

“They still view (Strange) as the strongest statewide incumbent," said Duffy. “He’s not a lightning rod. He’s not controversial. The appointment was; he’s not.’’

In addition to Trump and McConnell, other Republican members of Congress have stepped into the fray. Richard Shelby, the senior Republican senator from Alabama, recently endorsed Strange.

Moore has his congressional backers, too.

Rep. Mark Meadows, R-N.C., chairman of the conservative Freedom Caucus, and Rep. Jim Jordan, R-Ohio, a founder and member of the caucus, have endorsed Moore.

Alabama Rep. Mo Brooks, also a member of the Freedom Caucus, stepped up last week to back Moore. Brooks also ran in the special election primary, finishing third behind Moore and Strange.

Roy Moore talks to constituents before a Republican Senate candidate forum on Aug. 4, 2017, in Pelham, Ala.

Moore has also picked up support from former White House adviser Steve Bannon, Phil Robertson of Duck Dynasty and former Arkansas governor Mike Huckabee, whose daughter Sarah Huckabee Sanders is the White House press secretary.

The Senate Conservatives Fund, a political action committee that has endorsed Tea Party-aligned candidates against Republican incumbents, has endorsed Moore and so far has spent $255,000 in the race, according to its website.

Moore became a national figure in 2003 when he was removed from his position as chief justice of the Alabama Supreme Court for refusing to follow a federal court order to take down a Ten Commandments monument from a judicial building.

He was re-elected to that position a decade later but was suspended in May 2016 for ordering the state’s probate judges to not issue marriage licenses to same-sex couples even after the state same-sex marriage ban had been overturned.

Duffy said Moore and his supporters are on a mission to “beat the establishment.’’

“They all want to make a point with this race,” she said. “That’s why it has become so expensive. He’s running more against McConnell than against Strange.”

Duffy said it’s not unusual for the National Republican Senatorial Committee and the Senate Leadership Fund to support an incumbent, but the groups have had to spend a lot in Alabama to counter the support of conservative groups jumping in to help Moore.

The Senate Leadership Fund has spent nearly $8.5 million combined for the primary and the runoff, Pack said. The group had been willing to spend up to $10 million.

“We believe that Sen. Strange gives Leader McConnell the best opportunity to pass President Trump’s agenda in the Senate," he said.

But some argue national Republicans aren’t helping the GOP secure the seat in Alabama. 

And while experts expect the seat to remain in Republican hands, they say the race could be competitive especially if Moore faces Jones.

Brooks blames McConnell for recent polling showing a close race for the GOP candidates.

Brooks, who was also the target of the Senate Leadership Fund’s attacks, said historically a Democrat would have been expected to lose by about 20 points.

“The malicious nature of the Mitch McConnell attack ads is turning off independent voters and Republican voters with respect to our entire Republican field of candidates,” Brooks told reporters at the U.S. Capitol recently. “That has opened the door for a Democrat to win this election in the general election. While heretofore the Democrat would not have a prayer.”

Contributing: Brian Lyman and Eliza Collins