The Alabama GOP Senate primary on Tuesday will go a long way in answering the overriding question of the race: How much do Mitch McConnell’s cash and Donald Trump’s endorsement matter?

The brutal fight on the Republican side is all but assured to go to a September runoff, with no one expected to reach the 50 percent threshold to win the nomination outright. Sen. Luther Strange has the backing of Trump — who remains immensely popular in Alabama and cut a robocall for the senator on Monday — and millions in ads from a McConnell-blessed super PAC.


Even with that help, Strange isn't a lock to secure a spot in the runoff. Polls show ex-state Supreme Court Justice Roy Moore consistently leading, while Strange and Rep. Mo Brooks are battling for the runner-up position.

The polls close at 8 p.m. ET (7 p.m. local time). Here are POLITICO’s five things to watch as Moore, Strange and Brooks vie for the top two slots to advance to the Sept. 26 runoff:

Where does Strange land — and what does it mean?

With a massive cash advantage, powerhouse endorsements and the advantages of incumbency, Strange should be the front-runner. But swirling questions about how he was appointed to the seat by the disgraced ex-Gov. Robert Bentley have dogged Strange throughout his campaign.

“Luther Strange is the first opportunity voters have to put a head on a spike for all the corruption that’s been going on in Republican politics in the last three years," one former Alabama GOP official said.

Strange denies any impropriety and instead touts his record of taking on corruption as the twice-elected state attorney general.

But should Strange somehow not make the runoff — he's consistently placed second in polls, though the margin between him and Brooks is narrow — it would be a huge embarrassment for McConnell and establishment Republicans who have invested millions to help Strange secure the nomination.

Will Trump’s endorsement amount to anything?

In a race in which the candidates have tripped over each other trying to align themselves with the president, Strange can proudly claim he is Trump's man.

Trump announced the endorsement in a surprise tweet last week, tweeted again on Monday to boost the senator and recorded a robocall to help get out the vote on Election Day.

How much Trump’s imprimatur matters is unclear, but Strange isn’t hesitating to remind voters of it at every turn.

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To a crowd of Republicans in Homewood, Alabama last week, Strange recounted the phone call with Trump when he informed the senator of the endorsement, when the president told him: “I’ve never done this in a contested primary before, I’m sure I’m going to be criticized, but it’s important to get my agenda passed and I appreciate what you’re going through to get it done.”

“So, I can’t say anything more than what the president himself has said,” Strange told local party activists in the Birmingham suburb. “I hope you will bear that in mind.”

How high does Moore go?

Virtually every poll has shown Moore making the runoff by a comfortable margin. A trio of recent surveys had the judge leading the field with support in the 31 to 35 percent range.

Rep. Mo Brooks (left) is battling for the runner-up position in the Alabama GOP primary; polls show ex-state Supreme Court Justice Roy Moore (right) consistently leading. | AP Photos

Republican officials expect turnout to be low, which would likely hurt the rest of the field but potentially boost Moore, given his enthusiastic base. At the same time, Moore’s campaign is floating the idea that he could exceed expectations and win somewhere above 35 percent but probably below the 50 percent needed to clinch the nomination outright.

Moore’s campaign is also banking on Trump’s endorsement making only a marginal difference in the primary.

“I’m sure it’s got some effect on some people but I don’t sense the folks I’m talking to are being moved by it,” said Moore campaign chairman Bill Armistead. "I think the die is pretty well cast.”

What does the outcome signal for the runoff?

Strange is struggling even with the support of the president and the GOP establishment. Assuming he makes it to the runoff, though, the strength of his second-place finish will set expectations for how winnable the election is — or not.

If Strange barely makes it into the runoff — or comes in third — it will call into question the influence of Trump’s support in a reliably Republican state. If Strange exceeds the low 20-percent support he's gotten in recent polls, he'll still face a tough battle against Moore but won’t have to field a wave of questions about his ultimate viability or the power of Trump's endorsement.

What about the Democratic primary?

A Democrat hasn’t held a U.S. Senate seat in Alabama since 1997 but the party feels it might have an outside shot if the chips all fall its way.

Seven candidates are running for the Democratic nomination, but two are really in play: former U.S. attorney Doug Jones and Robert Kennedy Jr., a Navy veteran and business executive who’s unrelated to the Kennedy family.

Jones is the favorite of the Democratic establishment and has been endorsed by former Vice President Joe Biden as well as a handful of members of Congress. Democrats hope Jones’ civil rights records, including being the federal prosecutor who convicted two Klansmen involved in the 1963 16th Street Baptist Church bombing, and a chaotic Republican primary will create an opening for the seat.

A Raycom News Network and Strategy Research poll released in late July found Kennedy leading the Democratic field with 49 percent support and Jones in second place with 28 percent. This was before the endorsement by Biden, who has strong ties to Southern Democrats, but Jones’ campaign is still bracing for a tight election night and a likely runoff battle ahead.