Trump has endorsed only three candidates in seriously contested primaries today: Moreno, Bost and Merrin. With all three locked in competitive races, tonight's results could be a good signal of whether Trump's endorsement is as powerful as it used to be. We'll be tracking these races throughout the night.

—Nathaniel Rakich, 538

One of today's most consequential primaries for the general election is taking place in Ohio's 9th District. According to Daily Kos Elections, Trump would have carried the district 51 percent to 48 percent in 2020. But in 2022, incumbent Democratic Rep. Marcy Kaptur defeated Republican Air Force veteran J.R. Majewski 57 percent to 43 percent here thanks to Majewski's weaknesses as a candidate: He exaggerated his military service, attended the Jan. 6 rally (though he says he didn't enter the Capitol) and once subscribed to the QAnon conspiracy theory.

Majewski quickly announced he would run again in 2024, agitating Republican operatives who feared he would once again throw away a winnable House seat. But to their relief, he withdrew from the race a few weeks ago, leaving the primary to state Rep. Derek Merrin and former state Rep. Craig Riedel. Riedel was originally the top alternative to Majewski, but a couple of his pro-Trump supporters withdrew their endorsement of him after audio leaked of him calling Trump "arrogant." That sent GOP elders scrambling to find a new alternative to Majewski, and Merrin — who was in line to be the speaker of the Ohio state House last year until a faction of renegade Republicans joined Democrats to elect a different Republican — jumped into the race just before the filing deadline.

The primary is far from settled, though. While Trump endorsed Merrin just yesterday, and Speaker Mike Johnson endorsed Merrin in January, many establishment Republicans, such as House Majority Leader Steve Scalise and Majority Whip Tom Emmer, are still with Riedel. And Merrin's late entry into the race means he trails Riedel badly in fundraising, $175,000 to $1.2 million. And while he's no Majewski, a Riedel win could still give Republicans headaches: He's aligned with the tea party movement and has previously expressed interest in joining the hardline House Freedom Caucus.

—Nathaniel Rakich, 538

Chicagoans are voting today on a ballot measure pushed by progressives that would institute a real estate transfer tax to fund programs addressing homelessness. Today's outcome could tell us something about the strength of Chicago's progressive movement … and its unpopular progressive mayor, who's made it a policy priority.

According to publicly available polling, while Chicagoans may have started out feeling good about Mayor Brandon Johnson, their opinion quickly soured. According to Chicago-based Victory Research, Johnson's approval when he first took office in May was at 63 percent. Five months later, in October, Echelon Insights/Illinois Policy Institute found his approval to be just 28 percent, with 50 percent of voters disapproving of his job performance. By January, Tulchin Research/Stand for Children registered an approval rating of just 21 percent, with 70 percent saying his performance was "only fair" or "poor," while Echelon Insights/Illinois Policy Institute marked his approval at 29 percent and disapproval at 57 percent.

The January Echelon Insights survey also asked respondents if they approved of Johnson's handling of various issues facing the city. The mayor received the lowest ratings on "housing and homelessness" (20 percent approve, 68 percent disapprove), "management of immigrants transported to the city" (23 percent approve, 69 percent disapprove), and "crime and public safety" (24 percent approve, 66 percent disapprove).

—Mary Radcliffe, 538

As Geoffrey mentioned, Fong is the front-runner in today's California 20th special election, and there's a chance he wins the seat outright today if he gets a majority of the vote. Other than Fong, perhaps no one is rooting for this outcome more than House Speaker Mike Johnson, whose Republican majority is currently paper-thin — and getting thinner.

Right now, the House has 219 Republicans and 213 Democrats, meaning Johnson can afford two Republican defections to pass legislation with a bare majority (three Republican defections would yield a 216-216 tie, which isn't enough to pass a bill). However, GOP Rep. Ken Buck recently announced that he would resign on March 22, which will bring the GOP majority down to 218-213.

If Fong wins outright today, he would presumably be sworn in around the same time that Buck leaves, keeping the Republican majority at 219-213. But if he doesn't, the soonest Fong (or another resident of the California 20th) could take office would be late May following a runoff. And in fact, an April 30 special election in New York's 26th District is very likely to send a Democrat to Congress, which would narrow the GOP majority to 218-214 if the California seat is still vacant. That would mean that, for a time, Johnson could only afford one Republican defection before his bills would fail! If you thought it was hard for House Republicans to govern before …

—Nathaniel Rakich, 538

It’s midnight Eastern, and all but one of our key races have been projected in Ohio and Illinois. Here’s a recap of where things stand in those races:

- Former President Donald Trump once again flexed his muscles in the Ohio Senate race, elevating former car salesman Bernie Moreno from a 2022 also-ran to the GOP nominee in one of the two top Senate races on the map, beating an uber-rich state senator and a two-time statewide officeholder in the process. But Moreno’s toughest path lies ahead, against well-funded incumbent Democratic Sen. Sherrod Brown. With 96 percent of the expected vote reporting, Moreno leads with 51 percent of the vote over state Sen. Matt Dolan’s 33 percent and Ohio Secretary of State Frank LaRose’s 17 percent.

- In Ohio's 9th District, the conservative backed by Trump and House Speaker Mike Johnson, state Rep. Derek Merrin, is projected to win, and ready to take on Democratic Rep. Marcy Kaptur in what could be a tough general election race. With 80 percent of the expected vote reporting, Merrin has won 52 percent of the vote, 18 percentage points ahead of his nearest competition.

- In Ohio’s 13th District, another potentially competitive Democratic-held seat, former state Sen. Kevin Coughlin advanced out of the GOP primary rather easily and will take on Democratic Rep. Emilia Sykes in November. With 80 percent of the expected vote in, Coughlin leads with 65 percent of the vote so far over businessman Chris Banweg’s 28 percent and Richard Morckel’s 7 percent.

- The Republican Main Street Partnership notched a win against its rivals in the House Freedom Caucus in Ohio’s 6th District, where state Sen. Michael Rulli is projected to beat state Rep. Reggie Stoltzfus. Rulli currently leads by 9 points with 83 percent of the expected vote reporting in the regular primary, and by 8 points with 82 percent of the expected vote in the special election. Rulli will face a nominal challenge from Democrat Michael Kripchak on June 11 in the special election to replace Rep. Bill Johnson.

- In another safe GOP seat, Ohio’s 2nd District Republican primary went for business owner David Taylor, who won a crowded race that was tantamount to election in November. With 95 percent of the expected vote reporting, Taylor leads with 25 percent of the expected vote over 10 other challengers.

- Despite several challengers lining up to replace Democratic Rep. Danny Davis, the long-time incumbent is likely to hold onto his seat in Illinois’s 7th District. With 76 percent of the expected vote in, Davis leads with 53 percent of the vote so far. In second is Chicago City Treasurer Melissa Conyears-Ervin with 22 percent, followed by community organizer Kina Collins with 18 percent. Collins was seen as Davis’s primary competition tonight, and her underwhelming performance was part of a tough night for progressives in Chicago.

—Jacob Rubashkin, Inside Elections; Geoffrey Skelley and Monica Potts, 538