Until Nov. 8, no day will be more crucial than Tuesday in shaping the next Congress.

Voters in Florida and Arizona are set to cast ballots in congressional primaries, choosing party nominees for a host of open House seats and, in Florida, for districts that have been thoroughly scrambled by a court-ordered redistricting. Of Florida’s 27 House seats, at least seven will be filled by new faces in January, and as many as 15 could reasonably see turnover — a remarkable ratio for today’s Congress.

Both Republican Sens. John McCain (Ariz.) and Marco Rubio (Fla.) are expected to win their primaries against conservative challengers on Tuesday night.

In the Sunshine State, political watchers from Key West to Tallahassee on up to Washington are keeping close tabs on numerous primaries in both parties as a gauge of the crucial swing state’s mood. But it may take a careful eye to tease out the most important outcomes in light of the upheaval caused by the redistricting.

“It’s made drastic changes to the players, but the game itself hasn’t changed,” said David Johnson, a Tallahassee-based GOP consultant. “It’s still Florida, and it’s still very parochial. … It still comes down to odd things.”

Just a few months ago, the Florida Senate primaries looked to be marquee contests as each party maneuvered to fill the seat that Rubio pledged to vacate.

But in June, Rubio abruptly reversed course under pressure from national Republicans afraid that the seat was in jeopardy — perhaps along with the Senate majority. Rubio still faces a challenge from business executive Carlos Beruff, who has adopted a baldly Trumpian approach, but polls have shown the incumbent running well ahead of Beruff among likely primary voters.

On the Democratic side, a battle between two sitting House members — Reps. Alan Grayson and Patrick Murphy — looked like it would turn into a proxy fight between progressive and centrist Democrats.

But Grayson’s claim as a liberal firebrand was tarnished by domestic violence reports last month, while Murphy has largely weathered unflattering scrutiny of his resume to build a significant lead in recent polls. Earlier this month, Murphy stopped running ads, signaling that he’s conserving his war chest for Rubio

“The only question is, what’s the margin?” said Steve Schale, a Florida Democratic strategist.

The challenge to Rep. Debbie Wasserman Schultz (D) by college professor Tim Canova in the 23rd Congressional District has gotten intense national attention. But most Florida political watchers now expect Wasserman Schultz to survive despite Canova’s support from backers of Bernie Sanders presidential campaign dismayed about the incumbent’s former role as Democratic National Committee chair.

“Whatever Canova gets is sort of the remnants of the Sanders vote,” said Susan MacManus, a University of South Florida professor.

There is more drama Republicans are beating each other up in primaries to fill the open House seats of Murphy, Gwen Graham (D), Ander Crenshaw (R) and Curt Clawson (R).

Many of those races have been marked by the familiar national dynamic pitting establishment-vs.-insurgents — but with local twists. In the redrawn 2nd District,, surgeon Neal Dunn and lawyer Mary Thomas are clashing over their ties to former Gov. Charlie Crist — the Republican-turned-independent-turned Democrat who is a reviled figure among Florida conservatives.

A similar dynamic is at play in the Jacksonville-area 4th District, being vacated by Crenshaw, where former county sheriff John Rutherford is tangling with Hans Tanzler III, an attorney, and Lake Ray, a state lawmaker, over who is most thoroughly conservative.

In the Atlantic-coast 18th district, left open by Murphy, former school board member Rebecca Negron, wife of the state Senate president, is under fire for her establishment ties from outsider candidates, including Brian Mast, a wounded veteran touted by national conservatives.

In the 19th District seat left open by Clawson, Francis Rooney, former U.S. ambassador to the Vatican and a major GOP fundraiser, appears to have the upper hand over Chauncey Goss, son of former congressman and CIA director Porter Goss; and Dan Bongino, an ex-Secret Service agent who twice failed in Maryland congressional bids.

In the Miami-area 26th District, Democrats former Rep. Joe Garcia and businesswoman Annette Taddeo are locked in a tight contest. The winner will challenge incumbent Carlos Curbelo (R) in a seat at the top of national Democrats’ target lists.

Insiders are also keeping a close eye on Democratic primaries in the 5th district, where incumbent Corrine Brown is trying to overcome the twin obstacles of a major redistricting and a 22-count federal indictment; and in the 9th District, where Grayson’s wife, Dena, is seeking to replace her husband. She is battling Grayson’s former chief of staff, Susannah Randolph, and state Sen. Darren Soto.