WASHINGTON (TND) — The likely rematch between former President Donald Trump and President Joe Biden will move closer to being finalized this week as they will nearly have their party’s nominations locked up on the busiest day of primary season on Super Tuesday, when voters across more than a dozen states will cast a primary ballot.

Super Tuesday catapulted Biden toward the Democratic nomination in 2020 and put Trump in control of the Republican race in 2016. Both have essentially been able to campaign as incumbents even though Trump is not in office, which is setting up a night that is not expected to contain many surprises for the presidential race.

But there are also down-ballot races for House and Senate primaries that will play a big role in control of the government once the November election comes and could help decide which party has control of Washington until the 2026 midterms.

What to watch for on Super Tuesday:

WHAT STATES ARE VOTING?

Fifteen states will hold elections on Tuesday, the busiest day in primary season for both the presidential nomination and other down-ballot races.

Alabama, Arkansas, California, Colorado, Maine, Massachusetts, Minnesota, North Carolina, Oklahoma, Tennessee, Texas, Utah, Vermont and Virginia will have primaries for both Democrats and Republicans. Alaska will have a GOP-only primary and American Samoa will be voting for Democrats.

North Carolina is the only swing state with a Super Tuesday primary, while the rest have been solidly red or blue in recent election cycles. How particular demographics vote and how many of them turn out will offer some hints at how Trump and Biden are faring with voters in the state, which has voted Republican in the last two presidential cycles.

TRUMP NEARS CLINCHING NOMIINATION

The former president is projected to have a clean sweep of the GOP primaries on Super Tuesday, which will put him close to securing the 1,215 delegates needed to clinch the Republican nomination. More than a third of the delegates for Republicans are up for grabs and most of the states have a winner-take-all system, which helps Trump’s march toward the nomination.

He will not be able to clinch on Tuesday but will likely do so in the following couple weeks as a handful of other states hold their primary contests.

Trump’s campaign said it is expecting to have the nomination wrapped up in mid-March and has already turned its focus to running against Biden rather than targeting former United Nations ambassador and South Carolina Gov. Nikki Haley, the only remaining challenger.

Haley will face a decision of whether to keep her longshot campaign against Trump going, as she has only been able to win a primary in the District of Columbia to this point and is trailing significantly in national and state-level polls. She has vowed to stay in the race through at least Tuesday and potentially longer, but it’s unclear whether she will keep up the campaign or have the funds to do so long-term.

WHAT DOES IT MEAN FOR BIDEN?

Super Tuesday will be another test for the Biden reelection campaign’s strength among Democratic voters.

Biden is facing longshot challenges from Minnesota Rep. Dean Phillips and author Marianne Williamson, neither of which have been able to win a delegate to this point in primary season. He is projected to handily win all the delegates available on Tuesday, which will also inch him closer to wrapping up the nomination.

While he will still be the Democratic Party’s nominee, his campaign is also facing some pushback from some parts of the party over the death toll in Palestine as Israel and Hamas continue to clash. In Michigan, which has a high Arab and Muslim American population, more than 100,000 people voted “uncommitted” in the state’s primary instead of voting for the president.

Michigan has a history of “uncommitted” voting in Democratic primaries, but it was still a wake-up call for the president’s campaign and cost him the only two delegates he has lost so far. There are efforts to cast protest votes against Biden in a handful of Super Tuesday states, but none of them have gained the same type of traction as Michigan’s “uncommitted” effort.

CONGRESSIONAL PRIMARIES

Primary races for House and Senate seats will also happen in the 15 states involved in Super Tuesday voting, several of which have new congressional maps that will be more impacted by primary results with new, more competitive districts in a general election.

Alabama was forced to create a new congressional map last year by court order that adds another majority-Black district, adding an opportunity for Democrats to flip a seat in the ruby red state.

North Carolina also has new maps, which the Republican-controlled legislature drew to flip multiple House seats to favor their party in a general election. Some projections have Republicans winning up to 10 of the state’s 14 districts, a bump from the even split under the current map.

A wave of congressional retirements and realignments have also created open seats in states across the country that have crowded primaries, especially for seats that are solidly Democratic- or Republican-leaning.

CALIFORNIA SENATE PRMIARY

California’s so-called “jungle primary” will elevate two candidates, regardless of party affiliation to the general election in November for a Senate seat that opened with the death of longtime Democratic Sen. Dianne Feinstein.

Rep. Adam Schiff is expected to comfortably land one of the slots, but who receives the other is being closely watched. Republican Steve Garvey is fighting with Democratic Reps. Barbara Lee and Katie Porter for the other to take on Schiff in a head-to-head in November. Polling heading into Super Tuesday has Porter and Garvey running close to each other for second and Lee in third place.

Schiff’s campaign has sought to boost Garvey, as the state’s heavily Democratic voter makeup makes it a much easier contest for him to win than taking on a fellow Democrat.

Incumbent Sen. Laphonza Butler, who was appointed to the seat by Democratic Gov. Gavin Newsom, is not running in the race.