ATLANTA — There's a new front-runner in Iowa as the Democratic presidential candidates meet in head-to-head competition for the first time in more than a month at Wednesday night's MSNBC/Washington Post debate in Atlanta — but the national nomination picture is still stable.

Mayor Pete Buttigieg of South Bend, Indiana, riding a surge powered by his last debate performance and the cash he's pumped into building field operations in early states, has a 2.2-point edge over Sen. Elizabeth Warren, D-Mass., in the Real Clear Politics average of Iowa caucus surveys, with former Vice President Joe Biden and Sen. Bernie Sanders, I-Vt., trailing both of them.

At the national level, though, the standings haven't changed much. Biden's lead has narrowed to a 6.7 percent margin over Warren — 27 percent to 20.3 percent — in the Real Clear Politics average, with Sanders at 18.8 percent and Buttigieg at 8.3 percent.

This combination of campaign inertia and the failure of any one candidate to take a commanding lead after nearly 11 months of campaigning has helped convince two new candidates to enter the race, or consider doing so, in the last couple of weeks — former Massachusetts Gov. Deval Patrick, who is in, and former New York Mayor Michael Bloomberg, who may be — although neither had enough time to qualify for Wednesday's debate.

Amid all that, former President Barack Obama waded into the race last week to admonish Democrats not to overshoot with their policy goals, and House Democrats are conducting their second week of public hearings exploring the possible impeachment of President Donald Trump.

So there's a lot for these candidates to talk about. Here are five things to watch for.

Buttigieg may field some punches

When you're the front-runner in Iowa, you're going to get hit. Buttigieg's biggest strength and his biggest vulnerability right now are related: He's gaining ground in a state where 91 percent of the residents are white as he continues to struggle to win over voters of color.

The fact that the debate is being held in Georgia, where it is likely that more than half the Democratic primary voters will be black and more than three-fifths will be nonwhite, could put even more of a focus on Buttigieg's difficulty connecting with voters of color — as could the flub his campaign committed when it included a photo of a Kenyan woman on its website's plan for black Americans.

Between candidates fighting him for the votes of whites in Iowa and New Hampshire, and their efforts to make sure he doesn't gain traction with voters of color, Buttigieg can expect to be under fire.

A woman with a plan — that's changing.

Warren seems to have plateaued for the moment, and part of her challenge has been in explaining how she'll put in place a "Medicare of All" plan without raising taxes on the non-wealthy.

Obama's warning to Democrats seemed to be aimed at her and Sanders — even though he said in 2007 that he didn't want to wake up four years later in a country where millions of Americans remained uninsured — and she's now likely to face a new round of explicit criticism from moderates like Biden, Buttigieg and Minnesota Sen. Amy Klobuchar, and an implicit contrast from Sanders on her left.

Adam Green, a co-founder of the Progressive Change Campaign Committee, which has endorsed Warren, said she's "laid a trap" for anyone who wants to debate her on the details of policy, but some voters are going to want to hear why the woman with the plans has had to recalibrate with a new two-phase version of Medicare for All.

Plenty of pitches to black voters

Biden is the far-and-away leader among black voters in national polling and in South Carolina, the first state where African Americans will probably constitute a majority of the primary electorate. But he's still short of a majority in the polls, and most experts think there's opportunity for one or more of the candidates to make a move among black voters. On the heels of big Democratic wins in off-year 2019 elections that featured strong black turnout this month — and with black voters having played a pivotal role in the last two Democratic presidential primary contests — party strategists and voters want to hear how candidates plan to give a reason to continue that trend.

"With everyone competing for the most loyal voting bloc, how are you prioritizing this?" said Antjuan Seawright, a South Carolina-based Democratic strategist.

One (last?) chance to make an impression

For all but the top four candidates, who have the polling and funding to feel comfortable that they'll be competitive for awhile, this could be the final chance for the other White House hopefuls to showcase their stuff for voters nationwide.

In particular, that gives big incentive to three senators — Kamala Harris of California, Amy Klobuchar of Minnesota and Cory Booker of New Jersey — to stand out. That could mean finding a new way to define themselves in a positive light, but it more likely means punching up at one or more of the leaders in the field.

Rebecca Katz, a New York-based Democratic strategist, said the two women in that group may spend some time pointing out that they've done more to prove their mettle in more prominent jobs than Buttigieg.

"Harris and Klobuchar both have powerful incentives to compare their lengthy resumes in statewide and federal offices to Buttigieg's more limited credentials as the mayor of a small college town," Katz said.

Impeachment is the elephant on the stage

In the hours before the debate Wednesday, the House has held another set of impeachment hearings.

How the unfolding Ukraine drama plays into the case these candidates make for ousting Trump — and whether any of them will directly accuse him of trying to cheat in the 2020 election — could help shape voters' judgments about who is the strongest to take him on if he's not removed by Congress.