Loebsack is the second Iowa member of Congress to pick a side in the Democratic presidential primary: At the beginning of January, freshman Democratic Rep. Abby Finkenauer endorsed former Vice President Joe Biden. The endorsements may provide a credibility boost with some voters, but it’s unclear just how much they will affect the race in a state where the candidates have already spent months seeking votes in person and millions of dollars spreading their messages on TV and online.

Buttigieg and Biden are locked in a tight race with Sens. Bernie Sanders and Elizabeth Warren for first place in the Iowa caucuses, which will take place on Feb. 3. Sanders held a slight advantage, with the three other candidates within 3 to 5 percentage points of him, in the most recent poll of the state from the Des Moines Register/Mediacom/CNN on Friday.

Buttigieg posted another congressional endorsement recently: Rep. Anthony Brown (D-Md.), a fellow veteran and the first member of the Congressional Black Caucus to endorse the former mayor. But recent polling shows that Buttigieg continues to struggle with black voters generally, a longtime problem for his campaign.

While Buttigieg is competing at the top of the pack in Iowa and New Hampshire, he’s closer to the bottom of the Democratic primary in South Carolina, where he scored 4 percent in the latest survey from Fox News, including just 2 percent of black voters. Buttigieg also scored 2 percent among black voters nationally in a Washington Post-Ipsos poll.