Former President Donald Trump leads President Joe Biden nationally in a head-to-head race and in a deeper field as Americans say immigration problems at the border are worsening, according to Harvard/Harris polling.

The poll, published Monday, found Trump with a three-point advantage over Biden in a two-way contest at 47 percent to 44 percent. Another nine percent of respondents are unsure whom they will back:

Trump’s lead narrows slightly when undecided leaners are pushed to pick a candidate and are included in the total sample. In that scenario, he and Biden register at 51 percent and 49 percent, respectively. This is slightly down from Trump’s 53 percent to 47 percent edge in Harvard/Harris’s January and February polls.

Republicans are more committed to Trump than Democrats are to Biden. The president secured 82 percent of Democrat voters’ support before leaners were factored in, while 88 percent of Republicans backed Trump. Biden rose to 87 percent among Democrats with leaners included, while Trump climbed to 91 percent among Republican voters.

However, when leaners are accounted for, they are deadlocked at 50 percent with independent voters. Without leaners, Biden led with independents 42 percent to 38 percent.

Trump’s lead widens when third-party candidates are added into the mix. He takes 41 percent of support in a five-way race, followed by Biden at 36 percent. Independent candidate Robert F. Kennedy comes in third with 14 percent, while independent Cornel West and the Green Party’s Jill Stein tie at one percent. Six percent of respondents are undecided, and the margin between Biden and Trump remains at five percent with leaners included.

A collage of former President Donald Trump surrounded by Democrat, independent, and Green Party 2024 candidates, as well as President Joe Biden (AP: Alex Brandon, Matt Rourke // Getty: Frederick M. Brown, Michael M. Santiago).

Biden trails Trump as 58 percent of respondents say the “immigration problem at the borders” is worsening, and 73 percent want the Biden administration to “make it tougher to get in the U.S. illegally.” That includes 56 percent of Democrats, 88 percent of Republicans, and 78 percent of independents.

The Harvard/Harris poll sampled 2,111 registered voter respondents between March 20-21. A margin of error was not specified.