A single state could shift power in the Senate, where Democrats maintain a tenuous advantage by virtue of having the tiebreaking vote of Vice President Kamala Harris.
Thirty-five Senate seats are at stake in 2022, but the list of races considered competitive is much smaller. Most are in states that President Biden and former President Donald J. Trump contested fiercely in 2020.
A contentious Republican primary in Ohio
J.D. Vance, the “Hillbilly Elegy” author, has Mr. Trump’s backing among the many Republicans seeking to replace Senator Rob Portman, who is retiring. His rivals include Josh Mandel, Ohio’s former treasurer; Matt Dolan, a state senator; Jane Timken, the state party’s former chair; and the businessman Mike Gibbons.
On the Democratic side, Representative Tim Ryan, who has the support of Ohio’s other senator, Sherrod Brown, is a heavy favorite.
Big money and big names in Pennsylvania
A duel between two ultrawealthy candidates — Dr. Mehmet Oz, a celebrity doctor whom Mr. Trump endorsed, and David McCormick, a former hedge fund executive — has been the focus of the Republican primary to replace Senator Patrick J. Toomey, a Republican who is retiring. Kathy Barnette, a former financial executive, and Jeff Bartos, a real estate developer, are also seeking the G.O.P. nomination.
Democrats have several seasoned candidates, including Lt. Gov. John Fetterman, Representative Conor Lamb and Malcolm Kenyatta, a state representative from Philadelphia.
A key race in North Carolina
Several members of the G.O.P. rushed to fill a vacuum created by the retirement of Senator Richard M. Burr, a Republican who voted to convict Mr. Trump during his second impeachment trial. They include Pat McCrory, a former governor; Representative Ted Budd, who has been endorsed by Mr. Trump; and Mark Walker, a former congressman.
Cheri Beasley, a former chief justice of North Carolina’s Supreme Court and the first Black woman to have served in that role, is seeking the Democratic nomination.
The Georgia seat that was critical to Democrats
Herschel Walker, the Trump-backed college football legend, is the favorite among eight Republicans challenging Senator Raphael Warnock, whose victory in 2021 helped Democrats gain control of the Senate.
A test in Nevada for the first Latina U.S. senator
Catherine Cortez Masto, the first Latina senator, faces her first re-election test since her milestone victory in 2016. She is expected to win her primary, and in the fall, she is likely to face Adam Laxalt, a former Nevada attorney general endorsed by both Mr. Trump and Senator Mitch McConnell, the minority leader.
Republican challengers to Mark Kelly in Arizona
Senator Mark Kelly, a Democrat who won office in a special election, is seeking a full term. The Republicans who want the chance to stop him are Mark Brnovich, Arizona’s attorney general since 2015; Mick McGuire, a retired major general in the U.S. Air Force; Jim Lamon, a businessman; Blake Masters, chief operating officer of an investment firm run by Mr. Trump’s tech ally Peter Thiel; and Justin Olson, a member of the Arizona Corporation Commission.
A Democratic effort against Ron Johnson in Wisconsin
Several Democrats are trying to oust Senator Ron Johnson, a Republican whose approval rating has fallen amid an onslaught of television ads criticizing him for casting doubts about Mr. Biden’s election. They include Mandela Barnes, the lieutenant governor; Sarah Godlewski, the state treasurer; Alex Lasry, a vice president for the Milwaukee Bucks; and Tom Nelson, the top elected official in Outagamie County.
Trump’s move against Lisa Murkowski in Alaska
Mr. Trump endorsed Kelly Tshibaka to run against Senator Lisa Murkowski, who voted for Mr. Trump’s impeachment. Ms. Murkowski is seeking a fourth term.
Ms. Tshibaka, a former commissioner in Alaska’s Department of Administration, is trying to capitalize on right-wing antipathy to Ms. Murkowski, which was inflamed when she voted in 2017 to preserve the Affordable Care Act and in 2018 to oppose Justice Brett M. Kavanaugh’s confirmation.
The two Republicans will not go head-to-head in a traditional primary, however: Alaska’s primary is open to candidates and voters of any political stripe. The top four vote-getters will compete on a ranked-choice ballot in November, under election rules that were engineered by Ms. Murkowski’s allies.
A test of Marco Rubio’s strength in Florida
In Mr. Trump’s adopted state of Florida, Senator Marco Rubio is seeking a third term. He is likely to face Representative Val B. Demings, a Democrat with name recognition, this fall.
The New Hampshire Republicans (not) targeting Maggie Hassan
The dismal approval numbers of Senator Maggie Hassan, a Democrat, have emboldened the G.O.P.’s hopes of a pickup. But Republicans could not recruit Gov. Chris Sununu or Kelly Ayotte, whom Ms. Hassan unseated by about 1,000 votes in 2016. Several lesser-known Republicans have stepped forward, including Chuck Morse, the State Senate president, and Don Bolduc, a tough-talking retired Army general.