Spring is coming. This means the return of warm weather, flowers and competitive primaries. After Democrats notched wins over the winter in the special election for Alabama’s Senate seat and in Pennsylvania’s 18th congressional district, the change of the calendar means a change in the electoral landscape.

Starting with Tuesday’s competitive elections in Illinois – where a Democratic incumbent may lose his seat to a progressive challenger and a battle royale is shaping up for the governor’s mansion – the season will be filled with ferocious primaries as well as a special election caused by a congressional sexual harassment scandal. These are five of the most contested races coming up in the next few months.

Arizona

Democratic candidate Hiral Tipirneni, left, in Glendale, Arizona. Photograph: Ralph Freso/AP

Where: Arizona’s 8th congressional district special election

Who: Republican Debbie Lesko and Democrat Hiral Tipirneri

When: 24 April

Why It Matters: the special election on 24 April, which was prompted after longtime incumbent Republican Trent Franks resigned when he allegedly offered a staffer $5m to carry his child, will be the first held in the Sun Belt since Trump took office. Although the seat is not likely to change hands – Donald Trump won the deep red suburban Phoenix district by 21 points in 2016 – it will serve as more evidence of the GOP’s struggles in advance of the midterm elections.

West Virginia

Don Blankenship, a former mining CEO and candidate for the West Virginia primary. Photograph: Haraz N. Ghanbari/AP

Where: West Virginia’s Republican primary For US Senate

Who: mining executive Don Blankenship, congressman Evan Jenkins and state attorney general Patrick Morrisey

When: 8 May

Why It Matters: the Democratic incumbent Joe Manchin represents the state where Donald Trump did best in 2016 winning 68.5% of the vote. Republicans are desperate to take the seat and are currently in a three way primary that includes Evan Jenkins, a two-term congressman who is backed by Mitch McConnell, state attorney general Patrick Morrisey who backed by conservative groups like the Senate Conservatives Fund, and Don Blankenship, a former mining CEO who spent a year in jail on charges related to a 2010 mine disaster that killed 29 people. The winner in the primary will automatically become a focus of national attention as Republicans try to keep their slim majority in the Senate.

Texas

Laura Moser in Houston. The race has pitted the progressive against the Democratic establishment. Photograph: The Washington Post/Getty Images

Where: Texas’s Democratic primary runoff for the 7th congressional district

Who: attorney Lizzie Pannill Fletcher, journalist Laura Moser

When: 22 May

Why It Matters: the race has become a battleground in the fight between Washington Democrats and leftwing activists in a suburban Houston seat once thought to be safe Republican territory before Hillary Clinton won it in 2016. Fletcher has been embraced by groups like Emily’s List as the best chance for the party to win the seat. In contrast, Moser was the subject of an opposition research document released by the Democratic Congressional Campaign Committee (DCCC) before the first round of voting in an attempt to keep her from making the runoff. Instead, it backfired and rallied support from progressive activists to her campaign. The winner of the runoff will face incumbent the Republican John Culbertson in November.

California

Kevin de León is challenging California’s longtime senator Dianne Feinstein. Photograph: Denis Poroy/AP

Where: California’s non-partisan primary for US Senate

Who: state senate president pro tempore Kevin de León, Senator Dianne Feinstein

When: 5 June

Why It Matters: Feinstein, a Democrat who was first elected in 1992, is facing a challenge from the left from the top Democrat in the state senate. California’s unique top two primary system means that both are likely to advance to a general election in November. However, the first round of voting on 5 June will make clear whether the 84-year-old Feinstein will face a significant threat from progressives who have long been dissatisfied with her.

California

Dana Rohrabacher, the Republican incumbent of the 48th congressional district, is a controversial figure. Photograph: Bill Clark/CQ-Roll Call,Inc.

Where: California’s non-partisan primary for the 48th congressional district

Who: 15 candidates including incumbent Republican Dana Rohrabacher

When: 5 June

Why It Matters: Rohrabacher is a controversial figure who has long been known as the most vocal cheerleader for the Kremlin on Capitol Hill. Democrats have long seen him as vulnerable in November. However, due to the number of the Democratic candidates who are running against him, they may not get that chance. Scott Baugh, the former Republican leader in the California state assembly, entered the race late as a challenger to Rohrabacher. Due to California’s top two primary and the traditional Republican lean of the district, it’s possible that no Democrat could make the ballot in November. It’s one of several seats in California where a crowded Democratic field has left the possibility of the party being shut out in the general election.