INDEPENDENCE, Iowa — Endorsements in presidential campaigns often have little impact, but sometimes they do help to clarify priorities and choices as voters decide whom to support. That's the case of the endorsement former vice president Joe Biden got last week from a first-term House member from Iowa.

Biden has bigger names on his roster of supporters than Rep. Abby Finkenauer (D-Iowa). He has the backing of the Democratic Party’s 2004 presidential nominee, former secretary of state John F. Kerry. In Iowa, he has support from former governor (and former Obama administration agriculture secretary) Tom Vilsack and his wife, Christie. But Finkenauer’s endorsement is important for reasons beyond her own personal political standing or national recognition.

Her support for Biden, paired with the earlier endorsement of Sen. Bernie Sanders (I-Vt.) by Rep. Alexandria Ocasio-Cortez (D-N.Y.), crystallizes a strategic dilemma many Democratic voters are wrestling with a month ahead of the Iowa caucuses as they search for a candidate they believe can defeat President Trump in November: the choice between mobilization and persuasion.

The question still unresolved is if there is a candidate among the many running who can energize the party’s liberal grass-roots base to assure maximum turnout from key Democratic constituencies, while also being able to reach more-moderate swing voters to win back areas that Trump converted from blue to red in 2016. And if there is no candidate who can do both, which is the better path to victory?

Finkenauer and Ocasio-Cortez are the two youngest members of the Democratic House Class of 2018.

Ocasio-Cortez’s upset primary victory over former New York congressman Joseph Crowley in one of the country’s most liberal districts turned her into a national star and a symbol of the push from the grass roots to move the Democratic Party further to the left.

Finkenauer flipped a closely divided, Republican-held district in northeastern Iowa, helping Democrats capture the House majority.

Ocasio-Cortez’s endorsement of Sanders, made formal at a huge rally in New York in October, gave the senator a needed boost at a time when he was recovering from a heart attack and was struggling in the nomination contest. She chose Sanders and his democratic-socialist agenda over the other liberal in the race, Sen. Elizabeth Warren (D-Mass.). At the time, she said she wanted to help bring a “working-class revolution to the ballot box of the United States of America.”

Ocasio-Cortez is one of the most electrifying politicians in the country. There’s little doubt that a Sanders nomination, with her as one of his top surrogates, would energize many of the voters Democrats will need to win in November, especially younger voters of color and younger women, whose enthusiasm will be crucial to the party’s hopes of reversing some of the falloff in turnout that the party saw in 2016 when Trump defeated Hillary Clinton.

But the Sanders-Ocasio-Cortez combo also highlights fears among others in the party of a general election strategy that would leave many potential voters — independents, some Republicans and some moderate Democrats — feeling uneasy and potentially on the sidelines. That’s a risk many Democrats fear isn’t worth taking.

Finkenauer, who traveled with Biden through Iowa on Friday, has a different theme. “I did know, after the last year of being in Congress, that we desperately needed somebody in the White House who believed that we could bring people together again, because I spend most of my days in Congress where I am working across the aisle,” she said in an interview.

“There are other days,” she added, “where it’s like Democrats and Republicans are speaking different languages. And I think part of that is the fact that we don’t have the leadership at the top in the White House who believes it’s even helpful to bring people together.”

Finkenauer was interviewed Friday evening after appearing with Biden at a rally in Independence, Iowa, a town of about 6,000 people in Buchanan County in the state’s northeastern quadrant. In 2012, then-President Barack Obama won Buchanan County by double digits. In 2016, Trump carried it by double digits.

The pattern in Buchanan County is typical in Iowa’s 1st Congressional District. Of the 20 counties in the district, many of them rural and with small populations, 12 supported Trump after backing Democratic nominees for at least three consecutive elections. In some cases, the counties in Finkenauer’s district had voted for Democratic nominees for more than three straight presidential campaigns.

In 2018, Finkenauer defeated Republican Rod Blum by five points with 51 percent of the vote. Her victory — and how she won — is emblematic of what the 2020 Democratic presidential nominee must do in states running from Iowa, Minnesota and Wisconsin across to Michigan, Pennsylvania and even Ohio (perhaps the most difficult of all the states Trump flipped for Democrats to win back).

Finkenauer supported Biden’s 2008 presidential candidacy after learning about him from her grandfather, a firefighter. When her grandfather urged her to go see him back then, she said in her introduction of Biden on Friday evening, “I went, ‘Who?’ ” She came away impressed and said it is Biden’s record of working across party lines that drew her to endorse him in this campaign.

“He talks about that in his speeches, about how people think he’s naive to think that he can bring Democrats and Republicans together on certain issues,” she said. “You can’t bring people together on everything, but you at least have to have faith that you can find common ground and move things forward and you can start to heal our country. We can’t afford not to have faith in that. And he’s somebody who does.”

Biden isn’t the only candidate who makes unity a theme of his candidacy. Former South Bend, Ind., mayor Pete Buttigieg and Sen. Amy Klobuchar (D-Minn.) also talk about trying to unite a divided country and the importance of focusing on governing with the goal of getting results. Sanders and Warren favor bigger and bolder programmatic agendas and carrying on the fight against big corporations and wealthy power brokers.

Just as there are questions about whether a move-to-the-left mobilization strategy would leave Democrats short of victory, there are also questions about whether Biden as nominee would leave grass-roots activists and younger voters unenthusiastic and less likely to turn out to vote.

Many Democrats believe that Trump is all that the party’s nominee will need to assure maximum turnout in November. But still, they are nervous about the president’s capacity to win another electoral college majority. As Democrats get ready to start voting in a month, they are still looking for the candidate who can mobilize and persuade and aren’t sure yet who that is.