Democratic presidential candidate and mayor of South Bend, Indiana Pete Buttigieg responds to a question during a forum held by gun safety organizations the Giffords group and March For Our Lives in Las Vegas, Nevada, October 2, 2019.

Shifts in recent polls have shaken the top of the 2020 Democratic primary field, though the top contenders to face President Donald Trump have not changed with a little more than two months until nominating contests start.

South Bend, Indiana, Mayor Pete Buttigieg has climbed to leads in polling averages of the Iowa caucuses and New Hampshire primary, the first two contests in February, according to RealClearPolitics. Even so, former Vice President Joe Biden has kept his edge in surveys of the Nevada caucuses and South Carolina primary, the two other key early states.

Through the ebbs and flows at the state level, Biden has kept his grip on the national polling lead. While the surveys have their limits because voting takes place in states, they capture a broader snapshot of the race.

As voting finally approaches following months of campaigning, a four-person crowd has emerged at the front of the pack in national and early state polls. Biden, Sens. Bernie Sanders, I-Vt., and Elizabeth Warren, D-Mass., and Buttigieg have jockeyed for position as they try to differentiate themselves as the best candidate to take on Trump.