As the presidential election marathon breaks into a final sprint, the Trump campaign faces a jaw-dropping gap in the ground game: Hillary Clinton currently has more than three times the number of campaign offices in critical states than does Donald Trump.

The contrast is a test for the conventional campaign model and points to the candidates’ stark differences in methods. Clinton is cleaving to the data-driven, on-the-ground machine that won two elections for Barack Obama. Trump, on the other hand, insists he does not need traditional campaign tactics to win the election, pointing to his overwhelming nomination victory achieved with a relatively small team and little spending.

Nevertheless, the ground game is poised to be critical in 2016. Undecided voters are becoming scarce, and targeted turnout may be the deciding factor on Nov. 8. That usually requires field offices with phone banks, organized volunteers and a coordinated effort to knock on doors and get people to the polls.