So in at least three states where the Hispanic vote is expected to be higher than the national average — and a critical puzzle piece for Senate Democrats to take back control of the Senate — Senate Democrats have yet to to lock down the Hispanic vote. That’s a fairly big hill for Senate Democrats to climb with a little more than seven weeks to go.

Getting Hispanic voters, who make up some of the most transient, least-engaged part of the electorate, revved up about politics — let alone Senate races — is no easy task. Neither side has yet to figure out the formula.

In 2012, a majority of Latino voters didn’t cast ballots in the presidential election. A 2013 Pew Research analysis found Hispanics made up 17.2 percent of the nation’s population during that election, but just 8.4 percent of all voters. “Much of this difference is driven by the relative youth of the nation’s Hispanic population and the high number of non-citizen adults among its population,” the study authors wrote.

Senate Democrats need to net four seats in November (or five if Trump wins and Mike Pence is the Senate tiebreaker) to take back control of the chamber. They have a chance in roughly five to seven races. And in at least four of those, they’re counting on the Hispanic vote to help them get over the line.